Hmmm

I'd hate to be that guy… but genetically specking, breeding with your cousin doesn't have a serious medical impact in so long as you don't have a serious genetic disease.
Even then, it's only bad if you inherited it from the same side that relates you to your cousin. It could result in your child have a double dose of Huntington's disease or the like which would suck.

It's taboo for that reason, but really most people could get away with it with little consequence, especially nowadays where you can be screened for potential problems passed down. The more you know.

To be fair, it is taboo as a relatively recent thing. Historically, marrying your cousin was relatively normal. Marrying your sibling was always weird tho.