Ruth wasn’t related to Boaz, her mother-in-law Naomi was.
But anyway, you are right about birth defects in small tight communities. We see and hear of them in the Mennonite groups here, too.
Oh! Oh! That’s right. But Naomi said, “That man is *our* close relative; he is one of *our* guardian-redeemers” (They didn’t make a distinction, sometimes, between related by blood or related by marriage.) But Boaz still had to give some other guy first dibs on Ruth because thothe guy was more closely related (Ruth 3:12).
Cousins have the same grandfather. When grandpa dies, both cousins (married to each other) would be full joint heirs. Cousin-marriage is considered ideal by some landholding people because it keeps the property in the family.
Yeah, and genetic complications occur. Especially when the “pool” of people you’re eligible to marry, is small: as when religious subgroups form with only a small number of families. This sometimes occur amongst the Amish and Mennonites when a group with their “bishop” splits from the rest of the church, and the bishop wants them not to marry outside the group.
They are much more aware of it now, and are more apt to pore over genealogies or even agree to DNA analysis before deciding whether a particular marriage match-up is suitable.