Incest is legal if you are over 18 in some places
Also incest of Consanguinity is very different than incest of affinity
Let's say there was family A and family B
If a man from family A married a woman from family B
And then the brother of the man from family A married the sister of the woman from family B that would be incest of affinity and I do not think there is anything wrong with that
Incest of Consanguinity supposedly has a higher result of birth defects