Can You Marry Your Brother-In-Law?

That was a search that brought someone to this blog.

What is a brother-in-law?

There is more than one way to have a brother-in-law.

1) He could be your spouse's brother.

2) He could have married your sibling.

3) Some people would call a man who is married to their spouse's sibling their brother-in-law. For example, if I was married to a woman and her sister (who would be my sister-in-law) was married to a man, I might refer to him as my brother-in-law.

4) Similar to 3, someone might think of their sibling's spouse's brother as their brother-in-law. Your sibling's spouse is definitely your brother-in-law or sister-in-law. Their brother could thus be called your brother-in-law.

Unless "in-law" is being used figuratively or in the sense of number 4, it means you and/or he are married. In most places where English is the predominant language, people can still only be legally married to one person at a time. Where someone can only be legally one person at a time, the only way you can "marry your brother-in-law" is by being unmarried and marrying the person described in number 4.



This is more common, especially historically, than some people think, whether marriages have been arranged or have been chosen by the spouses themselves. With arranged marriages, the families already know each other from the previous matching. With spouse-chosen marriages, it is easy to meet and spend time with your sibling's spouse's sibling.

If both couples have children, those children are "double cousins" and are like genetic siblings.

There have even been situations in which identical twin men have married identical twin women.

So yes, in that sense you can legally marry your brother-in-law, and it happens all of the time. If you are a woman, you can legally marry your brother-in-law in more countries than if you are a man.

Where heterosexual polygyny is allowed as a legal form of marriage, an umarried woman can marry the man who is married to her sister, and thus she can marry her brother-in-law in that sense.

Where heterosexual fraternal polyandry is practiced, a woman is expected to marry her husband's unmarried brother (her brother-in-law) if she is going to have a polyandrous relationship.

Otherwise, currently, someone can only marry an ex brother-in-law, meaning that one or more divorces or deaths ends the marriage(s) that made him your brother-in-law.

With full marriage equality, you will be free to legally marry any brother-in-law who is agreeable. Won't it be nice when an adult is free to marry any and  all consenting adults, so that such questions won't have to be asked?

Regardless of all of he above, sex between in-laws does happen, both in affairs and in ethical nonmonogamy.