The NHS Would be Wrong to Stop Discouraging Cousin Marriage

According to the Telegraph, the NHS has been told to “stop discouraging cousin marriage”:

The National Child Mortality Database (NCMD) told NHS staff “it is unacceptable to discourage close relative marriage in a blanket way” because parents are only at a “slightly increased” risk of having a child with a genetic disorder.

It said genetic counsellors should meet the couple and their relatives to advise them on how to “consider arranging future marriages outside of the family”.

This has come at a time when the NHS has even sought a nurse to offer cousin marriage advice, though it’s not clear whether the purpose is to discourage or encourage the practice, or simply to avoid confronting people with the associated risks.

Unfortunately, the advice being given by NCMD appears to be missing a crucial point. The problems are much more serious in communities where cousin marriage occurs generation after generation.

The reader comments below the Telegraph article are obviously self-selecting but the views expressed tend to reflect a prevailing view that cousin (or consanguineous) marriages are a uniquely negative feature of the Pakistani Muslim community. They may be proportionately more common today than among contemporary indigenous British people but that rather glosses over how things were in former times.

Just a reminder that consanguineous (‘together, the same blood’) unions include, but are not limited to, incestuous unions. The term is normally now applied to cousin marriage but first appears in Shakespeare (Twelfth Night and Troilus and Cressida).

Obviously, first-cousin marriages are more likely to lead to problems because of having one set of shared grandparents and if that’s repeated then the likelihood of a child inheriting a defective gene is elevated with each generation.

In the 18th and 19th centuries cousin marriage was common in Britain, especially among the upper classes. One of the reasons was geographical proximity and limited social circles. People moved about considerably less and were therefore more likely to find their lives dominated by gatherings involving kinship groups. Another was economic. It was the best way of keeping money and property in the family and avoiding disputes. A BBC story points out that while cousin marriage is generally uncommon in the UK, that wasn’t the case in the past:

For most in the UK, the prospect of marrying a cousin is largely alien. But it wasn’t always so unusual. The father of evolution Charles Darwin married his first cousin, Emma Wedgwood. Their son, the Victorian scientist Sir George Darwin, went on to estimate that cousin marriages accounted for almost one in 20 aristocratic unions in 19th Century Britain. One of them was Queen Victoria, who married her first cousin, Prince Albert. The novel Wuthering Heights is full of fictional examples.

Here, incidentally, is one passage:

“My design is as honest as possible. I’ll inform you of its whole scope,” he [Heathcliff] said. “That the two cousins may fall in love, and get married. I’m acting generously to your master: his young chit has no expectations, and should she [Catherine] second my wishes she’ll be provided for at once as joint successor with Linton.”

Emily Brontë, Wuthering Heights, Chapter XXI

The possibility of the higher incidence of congenital defects or susceptibility to disease affecting those born from an incestuous or consanguineous union is well-known. One 2024 academic paper, reviewing the consequences of cousin marriage in Saudi Arabia didn’t pull its punches:

In Arab countries, especially Saudi Arabia, the rate of consanguineous marriage is high compared with Western European and Asian countries. This high rate is directly proportionate with elevated risk of genetic disorders, including congenital heart diseases, renal diseases and rare blood disorders. Additionally, it was noted that the rate of negative postnatal outcomes is higher in consanguineous marriages compared with the general population.

That study linked higher rates of cousin marriage and its problems in Saudi Arabia mainly to the least educated communities. And that’s really the point:

In Jordan, for instance, the consanguinity rate is inversely related to the educational level of the female partner; university-educated women are less likely to marry first cousins compared to their male counterparts.

In certain modern ethnic minority communities in Britain first-cousin marriage is securely attested, resulting in a congenital abnormality incidence of 6.5% compared to 2.5% in the general population, which on the face of it does not seem a huge difference in absolute terms (though does represent a relative risk increase of 160% i.e., well over double). That figure comes from a modern study in Bradford where, according to the BBC:

Researchers recruited more than 13,000 babies in the city and then followed them closely from childhood into adolescence and now into early adulthood. More than one in six children in the study have parents who are first cousins, mostly from Bradford’s Pakistani community, making it among the world’s most valuable studies of the health impacts of cousin marriage.

They found that even after factors like poverty were controlled for, a child of first cousins in Bradford had an 11% probability of being diagnosed with a speech and language problem, versus 7% for children whose parents are not related.

They also found a child of first cousins has a 54% chance of reaching a “good stage of development” (a government assessment given to all five year-olds in England), versus 64% for children whose parents are not related.

We get further insight into their poorer health through the number of visits to the GP. Children of first cousins have a third more primary care appointments than children whose parents are not related – an average of four instead of three a year.

The problem is not so much cousin marriage, but the practice of cousin marriages in successive generations, and it’s not restricted to Muslim communities in places like Bradford:

Prof Sam Oddie, a consultant neonatologist and researcher at Bradford Teaching Hospitals, has worked in the city for more than two decades. Over the years he has observed lots of severe genetic disorders. “I’ve seen fatal skin conditions, fatal brain conditions, fatal muscle conditions.” He says it was “immediately clear” these conditions were occurring more in Bradford than elsewhere.

But crucially, Prof Oddie thinks the main risk to genetic health in Bradford is not cousin marriage, but a similar issue known as endogamy, in which people marry members of their close community. In a tight-knit ethnic group, people are more likely to share common ancestors and genes – whether or not they are first cousins, he says.

Endogamy is not unique to Pakistani communities in the UK. It is an issue too in the UK’s Jewish community and globally among the Amish and also French Canadians.

“It’s often the case that the exact familial tie can’t be traced, but the gene occurs more commonly within a certain group, and for that reason, both parents carry the affected gene,” Prof Oddie says. “It’s an oversimplification to say that cousin marriage is the root of all excess recessive disorders in Bradford or in Pakistani communities. Endogamy is an important feature.”

Endogamy comes from two Greek words that mean ‘within marriage’, or perhaps better ‘marriage within [the community]’.

A couple of years ago I wrote a history of the Ptolemaic Dynasty that ruled ancient Egypt in its latter days. Incest in the Egyptian royal families has been a source of fascination from antiquity to modern times.

The Ptolemaic ruler Cleopatra VII’s lineage is well-known on her father’s line, even though none of the bodies have survived. She was the product of several incestuous unions. These included her paternal grandparents Ptolemy IX and Cleopatra V who were siblings, and her great-grandparents Ptolemy VIII and Cleopatra III who were uncle and niece. Even worse, Cleopatra III was the daughter of Ptolemy VIII’s siblings Ptolemy VI and Cleopatra II!

Despite that pedigree, Cleopatra VII (the famous one) was remembered in antiquity as a woman of extremely high intelligence, linguistic ability and charm, to which she added having several children by Julius Caesar and Mark Antony. She had previously been married to both of her younger brothers but had no children with them.

The Wars of the Roses, which afflicted England in the second half of the 15th century, are sometimes known collectively as ‘The Cousins’ War’ with good reason. Many of the protagonists were cousins by descent from Edward III (1327-77). Edward IV (1460-70, and 1471-83), was descended from Edward III’s fifth son Edmund, Duke of York. He was also descended from Edward III’s second son Lionel, Duke of Clarence. His daughter Elizabeth of York married her cousin Henry Tudor (Henry VII), he being descended from Edward III’s third son, John of Gaunt, Duke of Lancaster. They were the parents of Henry VIII.

Edward IV was, incidentally, over six feet tall and a highly successful military leader as a younger man. He died relatively young, but this appears to have been more to do with dissolute living. 

Just to add to the confusion, Edward IV’s mother Cecily Neville was the aunt of Richard Neville, 16th Duke of Warwick, who played a decisive role in the Wars of the Roses. His daughter Anne married Richard III. Through her mother, Cecily was the granddaughter of John of Gaunt and thus also descended from Edward III.

If that all sounds as if all this has nothing to do with you and cousin marriage is just to do with certain minority groups and decadent royal families, think again. If you are of indigenous British ancestry then it is, according to the geneticist Andrew Rutherford, “virtually impossible” not to be descended from Edward III. And, if that’s the case, that also means being descended from many other medieval monarchs, including ‘bad’ King John and William the Conqueror.

It means that programmes like Who Do You Think You Are? (BBC) that sometimes make such a song and dance about a random celeb being descended from, say, Edward I (127-1307), are completely (and deliberately) overlooking how unexceptional it is. I uploaded a talk to my YouTube channel about the episode featuring Josh Widdicombe and the claims made there.

Cousin marriage might have faded in most of modern British society partly due to improved education and other social and economic factors, but most of us are ultimately the product of cousin marriages at some point further back along the line, even if only through our shared descent from our mutual great (approximately times 30) grandfather, King Edward III. And if we could all trace our family trees in detail far enough back we’d find more cousin marriages.

The sustained frequency of consanguineous unions in a lineage is then the most important factor in causing congenital abnormalities to become embedded and widespread in a community with effects that are now statistically and indisputably measurable. It’s precisely because cousin marriage is less common now that the problems it causes have become more conspicuous in Britain or other places among those accustomed to perpetuating the practice.

If the NHS is going to tell anyone anything about cousin marriage and its potential consequences, that should be the message. Anything else would be utterly irresponsible and pussyfooting around the truth.

Guy de la Bédoyère is a historian and writer with numerous books to his credit, mostly involving Egyptian and Roman history, and the diarist Samuel Pepys.