Can you marry your brother-in-law? (Yes or No?)

In this article, we will answer the following question: Can you marry your brother-in-law? We also talk about the reasons behind falling in love with one’s brother-in-law and the point of view of religion. 

Can You Marry Your Brother-in-law?

No, you cannot marry your brother-in-law, if they are still married to your brother or sister, because that constitutes polygamy or bigamy, and these are not legal. However, if you want to marry your brother-in-law after the brother or sister has died or divorced them, it is legal to do so.

Can you marry your brother-in-law or sister-in-law?

In the UK you can marry your brother-in-law or sister-in-law, provided you are both over 21 years ago, and that neither of you is married. Polygamy is illegal. The law also states that you can not marry your brother-in-law if your sister is still alive. The same thing goes vice versa.

According to the Marriage (Prohibited Degrees of Relationship) Act 1986, the law prohibits certain blood relatives, step-relatives and relatives-in-law from getting married or registering as civil partners. Unless they fall within the exception below a person cannot marry or become civil partners with their:

  • Child
  • The adoptive or former adoptive child
  • Child of a former spouse or civil partner
  • Parent
  • Adoptive or former adoptive parent
  • A former spouse or civil partner of parent
  • Parent’s sibling
  • Sibling or sibling’s child
  • Grandparent
  • A former spouse or civil partner or grandparent
  • Grandchild
  • A grandchild of a former spouse or civil partner.


For the people mentioned in 3, 6, 10 and 12, there are some exceptions. They can marry if both parties are over 16 years of age, or register as civil partners if both parties are over 21 years of age, and the younger person was never a child in the older person’s family before they reached age 18.

“Child of the family”, concerning another person, means a person who:

  1. has lived in the same household as that other person and
  2. has been treated by that other person as a child of their family.

Since you and your brother-in-law are not blood-related, and if you meet the above criteria, no law forbids you to marry your brother-in-law. 

Marrying your brother-in-law

There was a time when brother-in-law marriage, in its two forms, sororate and levirate, was common. 

Sororate was the custom, according to which, the widowed man could substitute the deceased wife for his sister, marrying her. The levirate naturally assumed that the widowed woman would marry the brother of her deceased husband. In both cases, both the woman who married her sister’s widower and the woman who married her late husband’s brother had little ability to decide on the matter.

Seen with today’s eyes, this tradition would be an act of extreme violence against women, treated as mere merchandise and handed over to the man’s family during the act of marriage. The marriage between brothers-in-law was, in fact, a forced marriage, in which the patrimonial interests of the families prevailed over the will of the parties. 

Those were other times … Survival was more important than love, the authority of the parents was indisputable and women did not count.

Like we have step-brothers or sisters, many wonder if there is any such thing as a step brother-in-law.

Falling in love with your brother-in-law if your partner passed away is not so rare

Can you imagine being a widow and starting a relationship with your brother-in-law? Although it sounds crazy this is not new and is known as Levirate. From Macbeth’s novel, written by William Shakespeare in 1606, to a few days ago the relationship of Hillie Biden and her brother-in-law Hunter Biden – the son of former United States Vice President Joe Biden, in the Obama administration.

Hillie Biden is currently in a romantic relationship with Hunter Biden, the brother of Beau Biden, who died in 2015 of brain cancer. And it is that not only does literature touch on this subject, also the Jews in the Bible used to marry their widows (without children) with their brothers-in-law. 

This practice was known as the Levirate Law and said the following: “If two brothers share the same roof and one of them dies without leaving a child, the widow will not be able to marry any man from another family. Her husband’s brother must take her as his wife, and thus fulfil his brotherly duty. The first child that she gives birth will bear the name of the dead brother so that his name does not disappear from Israel. ” 

This quote appears in Deuteronomy 25: 5-10, in the Old Testament. 

The reason why this type of relationship occurs is due to the meanings of continuing to be united with the family after the loss. The family and the couple are in a duel, the severity and the impact it generates on them is in relation to the cause of death. Many times, being a sudden loss or a disease process where the family was very close to a partner, stronger bonds can begin to be generated. 

On several occasions, starting a relationship of this type can be through memories such as replacing or replacing everything that the deceased person of both parties meant. So now you know that the levirate has existed since Biblical times and it seems that the topic will continue to give us something to talk about, if it is not with the Bidens, it will be with other people because more than gossip it is a psychological process that can occur after the death of a person.

Forbidden love

Historically, forbidden love can be seen as a love that simply violates culturally dependent behavioural rules by turning into a secret love “that the world should not know about.” 

As Western civilization continues to progress along a socially libertine trajectory, many of the loves forbidden yesterday are no longer forbidden today, and others, such as interracial dating in America, are not explicitly forbidden but can be tacitly censored further (except for a few from the cultural margins). 

For a psychotherapist, psychologist or psychoanalyst, the concept that love could be intrinsically forbidden is not new. If you are a follower of Freud, everything comes from your first object of love (the parent of the opposite sex) which is dangerous outside its borders, but you do not have to be a Freudian to see that love can be dangerous in the life of a family. 

There is little doubt that parents and their children fall in love with each other, with the almost universal warning that in this context, love is separated from sexuality, but aren’t these two inherently close by nature? 

For example, no matter how absurd it sounds, isn’t it at least theoretically natural for a brother and sister to be attracted to each other when they reach puberty? And, in general, is it not expected that the intimate life of the family will lead to sexual feelings between its members?

When we are engaged in a forbidden love relationship the emotional depth is much greater and in addition to the need to resist this type of emotional depth we choose to see the reality of the obstacle (ie wrong religion, sex, age, marital status, etc.) rather than being entirely external and objective than that it is partially created by our perception and hesitation to legitimize our love.

So how do you know if you are guided by the “rebellious teenager inside” or the true love you should embrace?

Well, as with other types of failed love, sometimes you just have to be inside to win. In other words, the only way to find out is to eliminate all other external obstacles and let yourself be completely penetrated in your love. If then love dies, you know it was fueled only by rebellion.

 If you choose not to test it and thus continue the relationship you know that ultimately remains unacceptable to you or your partner, then by definition you are engaged in the pattern of forbidden love. It is also true that you will continue the relationship in secret to avoid family or social disapproval.

This logic implies, at least in theory, clarification on the dates you should avoid if you want to stay away from forbidden love. Avoid going out on dates with people you consider forbidden.

This rule requires that you “know” that you would never do such a thing, but can anyone know that? However, the better you know yourself, the more likely you are to avoid meeting someone you consider forbidden.

When you are not sure if a certain person is forbidden to you, you can do the following exercise: 

Imagine that you are married to this person, that you have a family with her, and what your relationship with your family of origin would be like ( mother, father, siblings …) with his / her family of origin, with friends.

 You can do the same exercise regardless of age, financial and professional status, and even if you never want to get married. The idea is to create the image of a public commitment that you can live with. 

So, in this scenario, regardless of the positive or negative reaction of the other important people in your life, would you choose the same thing? If your answer is yes, then considering the inner values that this person may not be forbidden to you.


In this article, we answered the following question: Can you marry your brother-in-law? We also talked about the reasons behind falling in love with one’s brother-in-law and the point of view of religion. 

In the UK you can marry your brother-in-law or sister-in-law, provided you are both over 21 years ago, and that neither of you is married. Polygamy is illegal. The law also states that you can not marry your brother-in-law if your sister is still alive. The same thing goes vice versa.

Hopefully, this article was of use to you. If you have any questions or comments on the subject, please let us know!

FAQ on can you marry your brother-in-law

Can you marry your sibling in law?

You cannot marry your sibling in law, since technically, he/she is married to your sister/brother. However, if this is not the case, you are not blood-related to your sibling in law, thus, you should be able to legally marry them. 

Is it a sin to marry your brother’s widow?

It is not a sin to marry your brother’s widow, but it also depends on what religion you have. For example, the Jews in the Bible used to marry their widows (without children) with their brothers-in-law. It was something that was expected of them.

What is it called when you are attracted to your sibling?

When you are attracted to your sibling, you may speak of Genetic sexual attraction. GSA means that a strong sexual attraction may develop between close blood relatives, but only when the two first meet as adults.

Is it illegal to sleep with your cousin?

In most countries, yes it is illegal to sleep with your cousin, parent, grandparent, sibling. 

References – Marriage (Prohibited Degrees of Relationship) Act 1986   -FORBIDDEN MARRIAGE LAWS OF THE UNITED KINGDOM -Forbidden Marriages