First cousin marriage in the UK is legal, but has long been contentious.
Richard Curtis wrote in the ending to Four Weddings and a Funeral that Tom marries his distant cousin Deirdre, having fallen in love at a wedding - a joke about the aristocracy supposedly keeping things in the family.
Despite the irreverence directed at the subject, marriage between cousins has long been argued against due to links to issues for children - a 2013 study found that children of first cousins had more than double the chance of potentially life-threatening birth defects.
Earlier this month, Baroness Flather told the House of Lords there should be a greater clampdown on the practice:
There are a lot of first-cousin marriages in certain communities, particularly among Pakistanis who come from the Pakistani Kashmir area.
We know so much about DNA now, but there is so much disability among the children, which is absolutely appalling.
It is a social practice which does not belong in today’s age, when we know so much about DNA. There should at least be some rule which says that you must have a DNA examination before your marriage can be registered.
Britain is not alone in allowing first cousin marriages - it joins the majority of Western countries in doing so, as the below map shows.Picture: Khin2718/Wikipedia, updated by indy100
Policy in the US ranges from legalised marriage between cousins and it being a criminal offence.
Last month it was reported that cousin couples in Tajikistan were racing to marry, ahead of the introduction of a ban.