Moral issue dating cousin
I love my brother, but this just goes against everything that I believe in.Extended family doesn't know about it, but my parents and siblings all do. Complicating things is that my second cousin has a history of being a manipulative user.If it wasn't the Ps & the Ss, then some other Jewish sects differed over it.Maybe it was the Hillel Pharisees vs the Shammai Pharisees.
Btw, IIRC, one of the differences between the Pharisees & the Sadduccees was if Uncle-Niece marriage was OK (I'm pretty sure Aunt-Nephew marriage was explicitly banned in Leviticus).
I'd be more worried about the personality traits you've described than the degree of consanguinity.
That is: Chances of genetic problems for a hypothetical neice or nephew are only slightly greater than if your brother were "dating" someone not related.
I can't fault him for that because she was a pretty hot and in really good shape from riding those horses. And not just third world countries, either; lots of industrial countries aren't squeamish about this.
BTW, those inspired by the fact that in many states first cousins are doable, remember: some of those states don't allow double cousins to get busy (double cousins = 2 siblings marry 2 other siblings, their kids are double cousins).