Prohibited Marriages

By in Legal Requirements, Wedding Articles | 3 comments

Forbidden Degrees of Relationship

Throughout the United Kingdom and the British Crown dependencies of Guernsey, Jersey and the Isle of Man, the law forbids certain blood relatives, step-relatives and relatives-in-law from getting married. These restrictions are officially know as forbidden degrees of relationship. The prohibitions apply to illegitimate as well as legitimate relationships. There are exceptions relating to certain step-relatives and relatives-in-law, which are explained later in this article.

A man may not marry his:

Mother (also step-mother, former step-mother, mother-in-law, former mother-in-law, adoptive mother or former adoptive mother)
Daughter (also step-daughter, former step-daughter, daughter-in-law, former daughter-in-law, adoptive daughter or former adoptive daughter)
Sister (also half-sister)
Father’s mother (grandmother)
Mother’s mother (grandmother)
Father’s father’s former wife (step-grandmother)
Mother’s father’s former wife (step-grandmother)
Son’s daughter (granddaughter)
Daughter’s daughter (granddaughter)
Wife’s son’s daughter (step-granddaughter)
Wife’s daughter’s daughter (step-granddaughter)
Son’s son’s wife (grandson’s wife)
Daughter’s son’s wife (grandson’s wife)
Father’s sister (aunt)
Mother’s sister (aunt)
Brother’s daughter (niece)
Sister’s daughter (niece)

A woman may not marry her:

Father (also step-father, former step-father, father-in-law, former father-in-law, adoptive father or former adoptive father)
Son (also step-son, former step-son, son-in-law, former son-in-law, adoptive son or former adoptive son)
Brother (also half-brother or step-brother)
Father’s father (grandfather)
Mother’s father (grandfather)
Mother’s mother’s former husband (step-grandfather)
Father’s mother’s former husband (step-grandfather)
Son’s son (grandson)
Daughter’s son (grandson)
Husband’s daughter’s son (step grandson)
Husband’s son’s son (step grandson)
Son’s daughter’s husband (granddaughter’s husband)
Daughter’s daughter’s husband (granddaughter’s husband)
Father’s brother (uncle)
Mother’s brother (uncle)
Brother’s son (nephew)
Sister’s son (nephew)

In Scotland, a man may not marry his great-grandmother or great-granddaughter and a woman may not marry her great-grandfather or great-grandson.

Other Prohibitions

You cannot get married in the UK or the British Crown dependencies of Guernsey, Jersey and the Isle of Man if either of you are under the age of 16. Please read our article on minimum age and parental consent for details of the parental consent requirements.

You must both also be free to marry, that is, not already married and you must also be of different sex at birth. This applies even if one of you has undergone gender modification surgery.

In England, Scotland and Wales (not Northern Ireland, Isle of Man, Guernsey and Jersey) the Marriage Act, 1986, allows for certain step-relatives and relatives-in-law to marry.


Step-relatives may marry provided they are at least 21 years of age. The younger of the couple must at no time before the age of 18 have lived in the same household as the older person. Neither must they have been treated as a child of the older person’s family.


Although a man may marry his sister-in-law and a woman may marry her brother-in-law, other relatives-in-law may marry provided they are at least 21 years of age and the family members involved in creating the in-law relationship are both dead. For example, if a man wishes to marry his daughter-in-law, both his son and his son’s mother must be dead. In England and Wales, marriages under this Act are not permitted with the calling of banns but can take place in a church on the authority of a superintendent registrar’s certificate without licence.

Marriage of Cousins

Despite the long list of degrees of forbidden relationship, you can marry a cousin (courtesy of Henry VIII who changed the law to marry his cousin!). However, it would be sensible for you both to consult your GP to ensure that there are no factors in your family’s health records that would make your decision to have children inadvisable on medical grounds.

Further Information

If you are still unsure of your situation and require further clarification of whom you can and cannot marry, please contact a registrar. You can usually find details of your local register office under the entry of Registration of Births, Deaths and Marriages in your telephone directory. Alternatively, you can telephone the relevant national office asking for the marriages section. Their telephone numbers are:

Registrar General for England and Wales, 01704-569824
General Register Office for Scotland, 0131-314 4447
General Register Office for Northern Ireland, 028-9025 2000
Registrar General for Guernsey, 01481-725277
Superintendent Registrar for Jersey, 01534-502335
General Register Office for the Isle of Man, 01624-687039

The above information was correct at the time of updating. Please check with your registrars office or relevant authorities for current information.

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If you still have any unanswered questions about prohibited marriages in the United Kingdom, please post your question on our Wedding Forum.

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  1. I know this is not in the same context, but a man CAN marry his daughter… If he is a vicar/minister.

    I of course mean “marry his daughter” as in the man, being of holy orders, can carry out the wedding ceremony at his daughters wedding!

    He certainly cannot marry his daughter in the context of him becoming the husband of his own daughter


    March 12, 2014

  2. Hi,can i marry my half sisters daughter in the uk.
    It doesn’t have to be a church wedding.
    If not can we go to somewhere like
    vegas and get married?

    Richard Kennedy

    March 25, 2014

  3. Uh, no. Even before the Marriage (Same Sex Couples) Act, couples did not have to be of different birth sex. Gender reassignment surgery DID make a difference. I read the legislation. If you were married and wanted to change your legal gender you had to swap your marriage for a civil partnership. Likewise, if you were in a civil partnership and wanted to change your legal gender you had to swap your civil partnership for a marriage.


    August 25, 2014

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