[bakul]

AFAIK this is far more common in muslims but not in hindus, jains etc. While growing up I had heard/read that as per the Vedas you can not marry someone with whom you have a common ancestor within 7 generations. [My scientifically minded atheist parents agreed with the idea.] Of course, in practice this isn't always followed but in any arranged marriage such proscriptions would presumably be checked.

[lazide]

Southern India has particularly low Muslim populations - and definitely doesn’t follow that guidance.

The vedas have many sections which get widely ignored.

Edit: HN throttling is terrible. Here is a link to a couple studies [https://pubmed.ncbi.nlm.nih.gov/32641190/], [https://www.researchgate.net/figure/Trends-in-consanguineous...]

AP has the highest rate, around 28%

[bakul]

I has asked friends who would know more about South India. If you have any references about statistics and causes please share. Thanks!

[abhinavk]

Cross-cousin and uncle-niece marriage is prevalent among Hindus in most states of South India (except Kerala). 10-25% of all marriages.

In religion, you can find your reasons for anything. e.g. In Mahabharata, Arjuna and Abhimanyu married their cousins.