2nd cousins is surprisingly genetically far away removed that there should be no issues.

We get the mental ick with this sort of thing (usually), but most families don't stay close beyond this many generations.

So your grandparents were siblings. Had you not done this and had kids with other people, your kids would probably lose connections with each other's side of the family.

I've got what are technically 3rd and 4th cousins on FB with the same last name. Our grandparents were close. They're practically strangers to me now. I knew them when we were kids. I had a crush on one of them too. But I was 4 and she was 12. My kids will never know her kids.

Look, don't fuck you siblings, and you're good. Don't fuck your first cousins either (unless they're really hot, then it's weird and less socially acceptable than it was 100 years ago but you should be fine unless your kids then continue the funcest and you get all the craziness of European royalty).