It was a prohibition that stood for 1,000 years – until one particularly capricious monarch decided otherwise.
In 1540, King Henry VIII changed the law to allow first-cousin marriage so he could wed Catherine Howard.
Since then, the practice has been legal in Britain, but a furore broke out this week when MP Iqbal Mohamed spoke out in defence of weddings between first cousins.
Tory MP Richard Holden is hoping to bring forward legislation that would ban such unions.
In the course of speaking out in the House of Commons, he told how Henry ‘broke with Rome’ so he could marry the woman who would become his fifth wife.
Although Henry was not related to Catherine Howard, she was a first cousin of his second wife Anne Boleyn, who was beheaded on the King’s orders in 1536.
According to the strict religious observance at the time, relatives of spouses were seen as being equivalent to actual blood relations of the other person in the union.
It meant that Anne’s cousins effectively became Henry’s when the pair wed in 1533.
In 1540, King Henry VIII changed the law to allow first-cousin marriage so he could wed Catherine Howard, his fifth wife. Although Henry was not related to Catherine Howard, she was a first cousin of his second wife Anne Boleyn, who was beheaded on the King’s orders in 1536
Mr Holden said in the Commons yesterday: ‘This 1,000-year tradition of first-cousin marriage being illegal was continued until 1540, when King Henry VIII broke with Rome and legalised marriage between first cousins so that he could marry Catherine Howard, his fifth wife and a cousin of his second wife, Anne Boleyn.
‘Sadly, both Catherine and Anne ended up facing a swift end at the block.
‘However, the law pertaining to first-cousin marriage has been more enduring, remaining unchanged ever since.’
Catherine Howard is portrayed by Summer Richards in the BBC’s adaptation of Hilary Mantel’s novel Wolf Hall: The Mirror and the Light, which is set to conclude this week.
Meanwhile, the view of the Catholic Church at the time was that marriage between first cousins was unacceptable.
The prohibition continues to this day but special dispensation can be granted by a bishop.
In 1560, during the reign of Queen Elizabeth I, Henry’s youngest daughter, Archbishop of Canterbury Matthew Parker formally codified what counts as a forbidden marriage in The Tables of Kindred and Affinity of the Church of England.
The list remained unchanged until 1907, when the Marriage Act of that year removed the ban on a husband marrying his sister-in-law, or a wife marrying her brother-in-law.
Catherine Howard is portrayed by Summer Richards in the BBC’s adaptation of Hilary Mantel’s novel Wolf Hall: The Mirror and the Light, which is set to conclude this week
Further updates in 1921 and 1931 removed prohibitions against spouses marrying their siblings’ former other halves and their aunt-in-law or uncle-in-law.
A final change in 1949 specifically included half-siblings in the list of banned unions.
Henry married Catherine Howard just 19 days after his marriage to fourth wife Anne of Cleves was annulled.
However, Catherine lasted for little more than a year before she was beheaded, on the grounds of treason for committing adultery with distant cousin Thomas Culpeper.
The King’s final wife, Catherine Parr, whom he married in July 1543, outlived him by nearly two years.
Anne Boleyn – the mother of Elizabeth I – was courted by Henry while he was still married to first wife Catherine of Aragon.
Henry had caused a rupture with the Catholic Church in Rome when the Pope refused to allow him to set Catherine aside so he could marry Anne.
Instead, the King made himself the head of the Church of England and appointed a new Archbishop of Canterbury, Thomas Cranmer, who allowed the annulment to proceed.
Mr Mohamed spoke out against Tory MP Richard Holden’s efforts to bring in new legislation to prohibit the marriage of first cousins
But Henry then became tired of Anne Boleyn when she proved unable to provide him with a surviving son.
So confected charges of adultery were brought against Anne. It was even falsely claimed that she slept with her own brother, George Boleyn.
Anne was beheaded on May 19, 1536.
Mr Mohamed, the MP for Dewsbury and Batley, told the House of Commons this week that many people view family intermarriage as ‘very positive’.
He said it was seen as something that could help ‘build family bonds’ and put families on a more secure financial foothold’.
Mr Mohamed admitted there were ‘health risks’ for the children of such marriages.
But he said a ‘more positive approach’ would be to ‘facilitate advanced genetic test screening’ for couples wishing to marry.
Mr Mohamed was speaking out out against Mr Holden’s efforts to bring in new legislation to prohibit the marriage of first cousins.
The former Conservative Party chairman introduced his Marriage (Prohibited Degrees of Relationship) Bill to the Commons via a ten-minute rule motion.
He warned there had been a ‘worrying trend’ of an increased rate of cousins marrying among some communities in Britain – although he noted there were reports of rates falling in the last decade as ‘young people push back against this system’.
Mr Holden outlined ‘health, freedom and our national values’ as three areas of concern over family intermarriage in the UK.
He urged the Labour Government to look as his Bill as a ‘vehicle for positive change in our country’, adding: ‘Because, in the end, it’s about more than one marriage – it’s about the values and foundations of our society and our democracy.’