Over the past few days I have been trying to figure out whether my sister-in-law's brother is my brother-in-law or friend? My friend believes we are not related anyhow i.e. if we were cousins his sister won't be marrying my first cousin which is wrong and the surname is not the same.

I am so confused as I researched on Google, coming up with different answers.

Not sure to mention this or not, but am having some kind of feeling towards him, I feel guilty thinking about it if we are technically related through marriage. The cultural context is India.

  • 1
    No country or culture that I know of would prohibit siblings from one family marrying siblings from another family.
    – Nigel J
    Jan 13 '18 at 22:17
  • It is India, they do not accept it at all. Thank you for replying though, appreciate it.
    – sunshine
    Jan 13 '18 at 22:44
  • @sunshine I don't know that we're talking about the same thing; see here.
    – tchrist
    Jan 13 '18 at 23:08
  • No it is not this, I understand where this is coming from. Some families I know allow this type of marriage to take place. My situation is that my first cousin is marrying my to be sister in law, and she has a younger brother - I am trying to establish a link we have related or not.
    – sunshine
    Jan 13 '18 at 23:11
  • You are not related to your cousin's wife's brother unless you are already related to those two siblings via some other relationship that has nothing to do with the marriage.
    – tchrist
    Jan 14 '18 at 1:06

Your sister-in-law is by definition one of two things:

  1. She’s your spouse’s sibling.
  2. She’s your sibling’s spouse.

In the first case, your sister-in-law’s brother is your brother-in-law, because in law the couple becomes as one person and he is your own spouse’s brother. However, in the second case, that sort of sister-in-law’s brother is not your own in-law.

But it really doesn’t matter either way. That’s because in neither case are you related to this gentleman by blood, and only in the first case by marriage. Since there is no blood relation, there can be no genetic argument against either of them even if you should be female.

Indeed it is perfectly common for one pair of siblings to marry another pair of siblings, provided that neither pair is already related to the other pair by blood.

Any issue from those two unions will be double-cousins to each other, so twice as related as a normal pair of cousins, the same has half-siblings. (Unless the pairs are identical twins; then the cousins are equivalent to full siblings.)

As for what is right and wrong here, that’s merely a cultural matter, and the answer varies according to which region you live in. Cousin marriage is extremely common worldwide, for example.

You are not related to your cousin’s wife’s brother unless you are already related to those two siblings via some other relationship that has nothing to do with your cousin’s marriage.

  • Thanks so much, for replying really appreciate it. I remember that my other first cousin is related to this person from his father's side as first or second cousin if am not wrong. I think I just answered my own question, making us related somehow?
    – sunshine
    Jan 13 '18 at 22:49
  • @sunshine It depends. The cousin of your cousin may not be related to you at all.
    – tchrist
    Jan 13 '18 at 23:00
  • I think were not related but just too embarrassed to ask close family and am sure he has picked up that I have something towards him, as we exchange messages he too directs to hints. Once again thank you so much.
    – sunshine
    Jan 13 '18 at 23:04

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