The term sister is often used figuratively to refer, for instance, to a “sister company” for a company within the same group, or to a “sister site” for sites that belong to the same family. This connotation as explained by the Cambridge Dictionary means:

  • belonging to a pair or group of similar and related things, such as businesses, usually owned or operated by the same person or organization:
    • our sister company in Australia.

also, from Collins Dictionary:

  • You can use sister to describe something that is of the same type or is connected in some way to another thing you have mentioned.
  • ⇒ ...the International Monetary Fund and its sister organisation, the World Bank....Voyager 2 and its sister ship, Voyager 1.

This usage appears to be common with things that are regarded as feminine and are associated, as if by kinship, with other similar things that belong to the same group. An early usage example of this is the "sister" referred to ships:

  • the US battleship Missouri and her sister ship, the Wisconsin.

In other instances, the "feminine" issue is less explicit as in the case of internet sites, so I guess this usage has to do with the fact that English is less gender specific when it comes to things or abstract entities.


  • Does “sister” apply to whatever entity that belongs to the same group irrespective of its real or perceived gender? or could "brother" be used instead?

  • Where does this usage come from?

  • 10
    FWIW, I've never heard brother used like this. And regarding your last line, companies or websites don't sound like particularly feminine things to me. Interesting question, though. +1.
    – Tushar Raj
    Commented Jan 24, 2017 at 11:14
  • 3
    I'll note that in carpentry, when a weak piece of lumber is strengthened by nailing another similar-sized piece to it, this is known as "sistering".
    – Hot Licks
    Commented Jan 24, 2017 at 12:53
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    @Lambie - I (native Br E speaker) see/hear nothing wrong with "ELU is a sister site to Engineering SE".
    – AndyT
    Commented Jan 24, 2017 at 15:54
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    Could perhaps use "brother site" as tongue-in-cheek thing if the web-sites both were very masculine and aimed towards men... That said, I suspect the reason is to emphasize that the sites are friends and co-operates rather than competing. While it's sexists and mostly a cliche; the relationships between brothers has often been described with a degree of competition and maybe hostility (think Cain and Abel), while that between sisters typically have not. So "brother-sites" may suggest a level of competition to many. Commented Jan 24, 2017 at 17:21
  • 3
    Possible duplicate of Why use the term "Sister sites" instead of "Brother sites"?
    – verbose
    Commented Jan 25, 2017 at 2:43

5 Answers 5


'Brother company' - or 'brother (anything)' - would almost certainly be considered incorrect (in English). There's no logical reason why it should be incorrect, only historical.

You're right that the first usage of "sister (object)" was probably for ships. I can't find anything earlier.

We use 'she' to refer to something which we have so much affection for that it almost seems rude to refer to it as 'it'. A common usage today is people referring to their cars as if they were female.

When this usage first arose, men dominated society and certainly dominated both ship-building and seafaring. Men, generally, have an affinity for women and so its only natural that they would start to use the pronoun 'she' for something that they were similarly fond of. For long periods at sea, men might feel nurtured by their ship - a quality that we generally associate more with women.

It's possible the usage directly transferred from ships to companies but I see this as quite speculative. It's a nice idea, though.

The first proper companies were formed to finance sea voyages. Each company was formed for a single ship voyage and dissolved at the end. Since the ship basically was the company, the usage of "she" for the ship transferred to the company itself. Thus we now have sister, daughter, etc. companies.

The user speedwell2

This is probably also at least partially a cultural thing. Other cultures do not necessarily want feminine qualities associated with their corporations. They would prefer for their companies to embody more traditionally masculine characteristics like strength and solidity. Supposedly in China companies are more often referred to as masculine, for example.

With a growing pressure to avoid using gender-specific language, I expect the usage of phrases such as 'sister company' to decline in favour of more neutral terms such as 'subsidiary'.

  • I agree that the usage probably derives from the custom of referring to a ship as "she", but doesn't "sister" applied to a website sound queer?
    – user66974
    Commented Jan 24, 2017 at 12:12
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    I don't personally think so. I guess this falls partially into the last sentence of my answer. If you wanted to avoid the gender aspect while staying on the same lines, you could use the phrase "sibling site". StackExchange is actually good example of this. They would refer to their other sites as "other sites in our network" or "other StackExchange communities" etc. Not as punchy, admittedly.
    – Michael
    Commented Jan 24, 2017 at 12:18
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    Well 'brother' is wrong and 'sister' you believe sounds weird, so you'll have to avoid using gender. Perhaps you could go for 'second cousin twice removed site'.
    – Michael
    Commented Jan 24, 2017 at 12:38
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    Brother company and they make printers, printers break, broken printers get you search engine entries..... And it's literally the first page of the search results. Please remove that part of your answer as it is highly misleading.
    – Helmar
    Commented Jan 24, 2017 at 19:16
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    You trust your life to a ship (or aircraft, or to a lesser extent car). Who would you (a male in a patriarchal society) trust your life to? A wife, maybe. A brother, maybe (but the story of Abel and Cain shows the other side). Is a sister the most likely relation to be unconditionally trustworthy? Also someone who founds a company probably has his financial life invested in it, and is spending more time on it than with his wife, so again the feminine pronoun?
    – nigel222
    Commented Jan 25, 2017 at 10:19

It happens that "sister" (and "mother" and "daughter") are used for relationships between various inanimate entities - ships, companies, schools, monasteries, languages - and not "brother" or "father" or "son". This is simply a fact about English, with no obvious explanation.

I'm dubious that this has anything at all to do with the use of "she" for ships and countries, but I may be wrong.

  • 5
    There's always an explanation, but the reason may be lost in time.
    – Mari-Lou A
    Commented Jan 24, 2017 at 15:21
  • it is also worth noting that small business owners would add "& Sons" to their shop/company name, but never "daughters". Do you know of any historical British companies whose name contain Last Name & Daughters?
    – Mari-Lou A
    Commented Jan 24, 2017 at 15:27
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    In terms of companies or relationships where ownership is implied, 'Parent' and 'Child' are now more common. However, in terms of side by side relationships, 'sister' is still far more common.
    – SGR
    Commented Jan 24, 2017 at 15:37
  • 1
    A search for "and daughter ltd" produces quite a few. There's one well known one in fiction, but it's hanging round the edge of my mind and I can't bring it into focus. Dickens, or perhaps Hardy. But it is comparatively unusual - for obvious reasons.
    – Colin Fine
    Commented Jan 24, 2017 at 15:37
  • The NOW corpus (current on-line English) has 24484 instances of "parent company", 1948 of "sister company", 276 "mother company", 31 "daughter company", and a handful of "child", "sibling", "brother" and "father". So @SGR you're right about "parent", but not about "child": "daughter" still occurs three times as often as "child".
    – Colin Fine
    Commented Jan 24, 2017 at 16:04

The answer as to why the term brother is never used in context with belonging to the same group, class, or organisation could lie in biology.

Women bear children, they are able to generate, and create new life. Likewise, if a company expands and creates (procreates) a new company, that "baby" company is related to its parent.

Sister cell

From Text-book of Botany: Morphological and Physiological, 1875, an illustration showing the protruding cell-wall containing the daughter-cells.

enter image description here

B the inner lamella of the mother-cell-wall which has entirely escaped (greatly enlarged).

SE Biology

During the days when philosophers used to debate, they tended to regard reproduction as a feminine trait. So naturally organisms/cells capable of producing offspring are also given a feminine trait. The parent cell is often called the mother cell, and the daughter cells are so named because they eventually become mother cell themselves.

It is no coincidence that a sister company is also called (less so today) a daughter company

Thus a sister site can be created or set up, and the main site is said to be the parent. Radio and TV stations, own sister stations and channels. This dispels the concept that the feminine pronoun is used as a term of affection. In a historical context, there is nothing cosy or affectionate about being ‘owned’ by a larger company, although it is in the parent company's best interest that their "daughter company" is equally successful.

sister company
A company which is owned by the same parent company as another company. One parent company can have one or many subsidiaries, which all are sister companies to each other. Business Dictionary

Sister Ships

An excerpt from The Naval Chronicle (including the biographical history of the Royal Navy of the United Kingdom), written in 1813, shows that the term sister ship was firmly established by the 19th century, also note the feminine pronoun used.

She is the sister ship [A French ship named Andromaque], in every respect, to the Weser; for their keels were laid down on the same day; they were launched the same day; sailed the same day ; were dismasted on the same day; were brought into Plymouth on the same day; and had a similar number of men, and weight of metal. The capture of these two vessels may perhaps be considered as doing Buonaparte a favour, inasmuch as it may spare him hereafter many unpleasant recollections attached to their names.

The excerpt illustrates perfectly the meaning of sister ship in that period. Today, the International Maritime Organization includes the following characteristics:

  • A sister ship is a ship built by the same yard from the same plans.
  • The acceptable deviation of lightship displacement should be between 1 and 2% of the lightship displacement of the lead ship, depending on the length of the ship.

The earliest example of sister ship I found on Google books, was its plural form, in a French-English Naval dictionary, titled Vocabulaire des termes de marine, printed in 1799.

enter image description here

All of which may appear to contradict my earlier statement, but I don't think it does. The term sister is derived from biology, and in the shipping industry, it refers to a ship built at a later date but following the same design and specifications as the "older sister ship". The parentage (mentioned by @BaconBits in the comments below) is the same, therefore any ship ‘created’ in the same yard, with the same hull, a similar weight, and equipment etc. is, in a figurative sense, a sister.

  • 4
    What about sister ship or sister city? That doesn't seem to follow your definition. It appears the term can be used for groupings of objects that are not necessarily in a hierarchy.
    – syntonicC
    Commented Jan 24, 2017 at 15:46
  • 5
    "Women bear children" - sure. That creates a parent-child relationship, not a "sister" relationship. If you have a holding company (say Holding Ltd.) and it has two companies that actually produce things (say Widgets Co. and Gizmos Inc.), then Widgets Co. and Gizmos Inc. would be sister companies, while Holding Ltd. is their parent company.
    – AndyT
    Commented Jan 24, 2017 at 15:50
  • Your biological assumption is very interesting, but how and when could that usage have moved from labs and scientific papers to enter common speech?
    – user66974
    Commented Jan 24, 2017 at 17:35
  • 4
    @syntonicC Sister city I'll give you, but sister ships still fits. Sister ships are typically those of nearly identical design and which often have been built in the same place at the same time and often in the same dock by the same shipbuilders. They could be said to be, "born of the same parentage."
    – Bacon Bits
    Commented Jan 24, 2017 at 20:58
  • 2
    @AndyT If you have a heirarchy of companies, one company may simultaneously be a sibling, parent and child (of different companies). If the mother-daughter analogy is used for parent-child relationships, then 'sister' is the most consistent term for siblings.
    – FLHerne
    Commented Jan 25, 2017 at 11:22

(Answering your question "could brother be used instead?") The OED says:

brother, n. IV. 10. A thing perceived as resembling, or having a close connection to, another or others.

with citations including:

a1475   (▸a1376)   Langland Piers Plowman (Harl. 875) (1867) A. ii. l. 141 (MED), Feire speche þat is feiþles is falsnes broþer.

1802   Wordsworth in Wordsworth & S. T. Coleridge Lyrical Ballads (ed. 2) II. 124   That April morn, Of this the very brother.

1830   Tennyson Isabel in Poems 8   A clear stream flowing with a muddy one, Till in its onward current it absorbs..The vexéd eddies of its wayward brother.

1911   Polit. Sci. Q. 26 164   In the United States, the telephone has grown to be the big brother of the telegraph.

1978   J. Maxwell America's Fascinating Indian Heritage iii. 97/2   The stickball game the Southeastern tribesmen aptly called the little brother of war.

  • Orwell's use of Big brother as a symbol of the regime had an altogether chilling effect on the reader. Having a close connection to a repelling symbol is right inline with doublethink. Commented Jun 16, 2017 at 17:24

The use of "sister" for a related item has been common since the 13th century, and seems to be independent of the gender of the noun.



IV. Something which is closely related to another thing.

9. Something having a close kinship or relationship to another; something belonging to the same class or group. Sometimes personified.

See also appositive uses with the sense ‘fellow’.

a. With reference to an immaterial thing, esp. a quality, emotion, or behavioural trait.

a1225 (▸c1200) Vices & Virtues (1888) 29 Of rihte ȝeleaue. All ðat hire suster, ðe rihte ȝeleaue, hire seiȝeð, all hie [sc. hope] hit fastliche hopeð1. [Of True Faith: All that her sister, true faith says to her, she sincerely trusts it.[2]]

b. With reference to a material thing, place, etc.

a1500 (▸c1477) T. Norton Ordinal of Alchemy (BL Add.) (1975) l. 2320 (MED) Quycsyluere..wil nevir cleve to a thing But to metal of oone kind or odyre, For there he fyndith sustir or brodyre. [Quicksilver (mercury)... will not stick to anything except to a metal of one kind or another, for thatis where he will find a sister or brother.]

1580 T. Crewe tr. G. Meurier Nosegay of Morall Philos. sig. F3 Q. Who is sister to death? A. Sleepe.

2005 Independent (Nexis) 5 Feb. 45 The drink incorporates creme de mure (blackberry liqueur), the somewhat sweeter sister of creme de cassis (blackcurrant liqueur).

Sister, in this [attributive] sense thus pre-dates the nautical influence.

†10. Nautical. Any of various items of tackle having two or more matching components.


1410–12 in N. H. Nicolas Hist. Royal Navy (1847) II. 475 Un rakke ove ii. sustres, un trusp'aill ove ii. sustres, ii. slenges, un trusse, un canon.

NB: by this time, (i) nouns had lost their gender. (ii) The Old English noun "scip" (ship) was not feminine - it was neuter https://bosworthtoller.com/57769

1 Of feste hope. HIER after cumþ an oðer hali mihte ðe is iclepedfirma spes, þat is, fast hope to godalmihti. All ðat hire suster, ðe rihte ȝeleaue, hire seiȝeð, all hie hit fastliche hopeð.

[2] my translation

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