Gee, that kid is gonnz have a swell time growing yp not knowing which tein their loose mother slept with fathered them.
Such a bizarre situation. He’s for sure closely related to both of them, but won’t know who is Uncle and who is Dad. Likewise for them, they know the kid is definitely either their nephew or son...but have no way of knowing.
Another of infinite reasons why sleeping around is destructive behavior, and not just to those directly involved in said behavior.