Fraternal twins is what you call a set of twins who look different, but the word fraternal also has the meaning 'of or relating to brothers', and comes from a Latin root meaning 'brother'.

The question is, how do I refer to a set of twins who look different but are both girls? May I use the phrase sororal twins to describe them? Or can fraternal be used here, too?

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    This seems easily answerable by looking up sororal in a dictionary, or even just putting the word into Google, which would give multiple examples of the word being used. Is there any reason you doubt its validity? Commented Sep 7, 2023 at 0:13
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    @Heartspring Thanks. I've edited it to describe exactly what prompted my question.
    – Geremia
    Commented Sep 7, 2023 at 0:34
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    'Dizygotic (DZ) or fraternal twins (also referred to as "non-identical twins", "dissimilar twins", "biovular twins", and, informally in the case of females, "sororal twins") usually occur when two fertilized eggs are implanted in the uterus wall at the same time.' Source: en.wikipedia.org/wiki/Twin. This question is GR, easily found, but sororal twins is not common (SE, USA). Commented Sep 7, 2023 at 4:28
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    Best answer in such cases is usually to ask them what they prefer to be called.
    – Stuart F
    Commented Sep 7, 2023 at 8:32
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    'Fraternal twins' is a fixed expression with a non-default stipulative definition of 'fraternal' if one decides to deconstruct. Wikipedia states that the corresponding expression for two non-identical female twins 'sororal twins' is used but only in informal registers. 'Fraternal twins' may be used as a blanket term for any pair of non-identical twins [The Oklahoman], including girl + boy. Commented Sep 7, 2023 at 15:07

1 Answer 1


Informally, the term "sororal twins" is used:

To Become a Priest: A Love Storybooks. Den Adler · 2007

Patrick shot her a look. “A sore what?” “Sororal twins. It means sisterly, like fraternal means brotherly. It's in the dictionary. I looked it up.” “There are no such things as sororal twins,” Patrick said. Jessica stuck out her tongue.

Your Own Neuron: A Tour of Your Psychic Brainbooks. Abhijit Naskar 2015

Figure 3.1 Monozygotic and Dizygotic Embryo Formation Dizygotic or non-identical twins (also known as "fraternal twins", "dissimilar twins", "biovular twins", and, informally in the case of females, "sororal twins") usually occur when ...

Formally, it is not:

Encyclopedia of Genetics, Genomics, Proteomics, and Informatics PAGE 714 George P. Rédei · 2008 one or both of the twins are girls (in the latter case, the biologically correct usage should be “sororal twins” but it is not used).

Fertility and Pregnancy: An Epidemiologic Perspective - Page 306 Allen J. Wilcox · 2010

Tubal pregnancy (see Ectopic) Twins, Dizygous (Fraternal) Two infants in the same pregnancy who arise from two separate ova (which raises the question of “sororal” twins or “trizygous” triplets, neither of which term is used.)

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