Lots of inbreeding among Hasidic Jews and lots of kids with disabilities.
I guess its quite common in the closed and tribal communities.
For hundreds of years, Ashkenazi Jews intermarried with cousins. Royals just had a smaller pool to play in, but many people throughout history married cousins. Some of my German lines (they were Catholic), married cousins. Probably same with some of my Polish ancestors in one small village who seemed to all be related to each other.
lots of inbreeding i nthe middle east- and the side effects are devestating - just watched youtube vid on how more than 1/2 of british pakistanis engage in interbreeding and what it does to them- blind, deaf, etc
https://www.youtube.com/watch?v=kyNP3s5mxI8