Midwives have been told about the benefits of “close relative marriage” in training documents that minimise the risks to couples’ children.
The documents claim “85 to 90 per cent of cousin couples do not have affected children” and warn staff that “close relative marriage is often stigmatised in England”, adding claims that “the associated genetic risks have been exaggerated”.
Lots of things lead to increased risk of birth defects, like having children after the age of 30. I thought it was pretty well known that the risks associated with inbreeding drops off pretty sharply at the cousin level? At that point I think the appropriate reaction is social stigma, but not legal ramifications.
It also compounds over generations; if you’re the child of first cousins, you really should seek someone who it would take genealogy research to find a common ancestor with. If you’re not, it’s still a serious risk to have kids with anyone too closely related, but level ramifications seem really harsh, especially thinking of situations like adoption where someone could end up there accidentally. And to your point, it isn’t the only way to end up with that kind of risk profile.
We are talking of a huge difference between risks to a child by parents over 30 compared to a clear 15% risk with cousins having children. The actual risks are higher where there are recent (parent and grandparents) who were also more closely related.