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.

Read More: The NHS Would be Wrong to Stop Discouraging Cousin Marriage