Can a brother and sister marry in the UK?

Short answer

No, a brother and sister cannot marry in the UK. The law prohibits marriage between close blood relatives, including siblings, half-siblings, parents and children. Such marriages are not legally recognised and cannot take place.

In the UK, the law bans marriage between close blood relatives. This includes full siblings, half-siblings, parents and children, and also extends to some other family relationships like uncles, aunts, nieces and nephews. The rules apply across England, Wales, Scotland and Northern Ireland. A marriage between a brother and sister would be void, meaning it has no legal effect from the start.

The reason for this law is to prevent genetic risks to any children and to maintain social and legal norms. There is no way to get an exemption or special permission for a sibling marriage. If you are in this situation, the marriage cannot go ahead, and you should not attempt to give notice or book a venue.

If you have questions about whether a particular relationship is allowed, you should ask the registrar at your local register office. They can advise on the legal position. The rules can vary slightly between different parts of the UK, so it is best to check with the relevant authority. For any legal detail not covered here, check GOV.UK or speak to a registrar.