• Forbidden Marriages

    Prohibited Marriages

    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.
    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.


    Exceptions for Certain Step-Relatives and Relatives-in-Law
    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
    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.

    Relatives-in-Law
    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.

    It is permissible for a man to marry his mother in law as long as his wife is deceased - its the same principle as a man wishing to marry his daughter in law --- both his son and the man's wife must be deceased.

    These marriages cannot take place in a church but are allowed in a register office:


    The 1907 Marriage Act removed no. 17 from the original forbidden list (Wife's sister and Husband's brother) provided the first spouse in each case was deceased.

    Further changes followed in 1921, 1931 and 1949:

    The 1921 Marriage Act removed no. 18 (Brother's wife and Sister's husband) provided brother or sister in each case was deceased.

    The 1931 Marriage Act removed 6, 7, 8 and 9 (Aunt-in-law and Uncle-in-law) and 27, 28, 29 and 30 (Niece-in-law and Nephew-in-law) provided the relevant Uncle, Aunt, Niece, and Nephew were dead.

    The 1949 Marriage Act confirmed the previous 3 acts and specifically included 'half blood' relatives.


    This website also explains the Forbidden Marriage Laws of the United Kingdom




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