You probably have hundreds of fifth cousins. The chances of sharing any DNA with him are remote, and what there is would be very slight. Don't worry about it, your kids are fine.

5th is removed enough that it doesn't matter. My 3rd cousins alone are about 1000.

that's as genetically similar as a stranger who cares?

There are those who argue that first cousins can marry and not beget a brood of r-words. Fifth cousins is so distant, no one in Alabama would be impressed.

If your children came out alright then no need to worry. js

I remember reading somewhere that odds are you could point to any random stranger in your hometown area and you'd probably be 4th cousins or similarly related. First-cousin marriage doesn't generally immediately lead to genetic issues accumulating, as long as the practice isn't repeated over several generations and such, and most regions have zero restrictions at all on second cousins marrying, because by that point your gene pool is reasonably far apart. Fifth cousin is a less-than-tangential relationship. And presumably you weren't raised together or anything, so it isn't like realizing you married a relative you lost contact with long ago or something. If you go back far enough, all of humanity is some degree of cousin with one another. Who knows? Maybe most of us are in relationships with a 10th-cousin twice removed or something (It's almost certainly a closer relationship than that).

Fifth cousin? That's hardly even worth noting. You probably have many cousins with that same degree of separation

Everybody in the world is related to each other within a few generations. 5th cousin is a genetic stranger. You have to go back 6 generations to have a direct match.