Britain’s National Health Service is facing a revolt for touting the “economic advantages” and “stronger extended family support systems” of marriages between first cousins. Britons, despite crackdowns on free speech, are rallying to protect their culture from the problems of family trees that don’t fork — a side-effect of mass immigration.

A member of parliament, Richard Holden, tells The New York Sun that first-cousin marriage “is hugely damaging to individual freedom and women’s rights and has massive health implications.” He called it a “disgrace” that the NHS is “actively promoting it.”

The row began last week when the NHS questioned the United Kingdom’s ban on brides and bridegrooms with the same grandparents. “Practiced for centuries across many cultures,” the agency wrote, such unions are “often seen as a way of preserving family wealth, strengthening social ties, and maintaining cultural traditions.”

Endorsing the taboo led the NHS to delete its missive on Monday. “I’m glad they’ve taken the web post down,” Mr. Holden said. “But, I fear, attitudes around cultural relativism persist and are pervasive right across too many parts of the state and society — and need to be challenged wherever they arise.”

In “The Case for Banning Cousin Marriage,” published on May 31, 2024, in the Oxford Journal of Law and Religion, Patrick Nash advocated “the universal case for banning” consanguineous marriage, “regardless of jurisdiction or culture,” on health and societal grounds.

Mr. Nash, who holds a Ph.D. from the University of Bristol, laid out his arguments for the Sun. “There are plenty of historical facts to back up the benefits of banning” first-cousin unions, he said, citing “Weirdest People in the World,” by a Harvard professor, Joe Henrich.

Joining different families “breaks up clans,” Mr. Nash said, “ends honor culture, fosters institution building, reduces corruption, and so on.” Asked about reluctance to legislate issues related to sex, he explained that the debate “tends to ignore this aspect.” But “the social/moral/cultural case for banning cousin marriage is just as strong.”

The NHS argued that “U.K. laws allowing first-cousin marriage date back to the reign of Henry VIII in the 16th Century,” though he married a cousin of his former wife, Anne Boleyn, not his own kin. It’s “not really true,” Mr. Nash said, “that cousin marriage was common amongst the British aristocracy.”  

At its Victorian peak, “only 5 percent” of royal marriages were among close cousins, Mr. Nash said, and “Queen Victoria’s children were badly affected by blood disorders.” Like President John Adams and his wife, Abigail, “Queen Elizabeth II and Prince Philip were only third cousins … virtually the same as two unrelated people.”

The Austro-Hungarian Empire’s Hapsburg Dynasty, Mr. Nash said, is “a good case of incestuous royal lineages which destroyed the cultures and states they ruled.” Children born of incest suffered from “low IQs,” leading to an “inability to rule effectively due to genetic illnesses.”

Those factors contributed to Austria-Hungary’s designation as “the sick man of Europe” in World War I and hastened its collapse. Marriage between relatives, Mr. Nash said, also “perpetuates the formation of clans/tribes which behave extremely aggressively to outsiders and punish internal dissent violently,” including “honor killings” of women.

Because arguing for a ban on consanguineous marriage condemns the cultures of African and Muslim communities, the dissenters could incur the wrath of U.K. authorities if it’s deemed “hate speech.” But Britons have been fearless about speaking out, judging the issue as falling well outside the bounds of the state’s demand for tolerance.

“There has been an enforced fear,” Mr. Nash said, because on “religious matters, violence or the threat of it tends to discourage people from speaking.” He cited the U.K.’s “de facto blasphemy law … policed by fanatical vigilantes.” On this issue, however, concerns have “more to do with professional ostracism in the medical and academic professions.”

Opponents of first-cousin marriages are letting loose the British lion’s roar in defense of a threat to U.K. culture and national health. “The taboo,” Mr. Nash says, “has now been broken,” and the NHS retraction “will hopefully lead to much more open research and discussion” of incest’s costs to society.