"What if they're cousins instead"

Why hasn't God controls for ignorance of blood relation and conception?

In its first chapter, the Christian Bible suggests that we are all incestuous descendents of Adam and Eve and their children.

"You are all inferior"

Is God benevolent if there is accidental conception by incest, and it genetically damns the sinless child and multiple generations of their progeny by design?

Anything closer than first cousins risks the health of the child.