While re-reading Luke a question popped up regarding the relationship between John the Baptist and Jesus. How could they be cousins if one was from Levi and the other Judah? Had marriage between tribes become a more normal occurrence? Or just an accepted practice in Judah after the split from Israel.
Since Levi and Judah were brothers, all their respective descendants were cousins. In Luke 1:36 (KJV) Elizabeth is called Mary’s cousin. If she and Elizabeth were cousins, then Jesus and John would have been cousins as well.
Marriage between the tribes was only forbidden in cases where tribal inheritance would be jeopardized. (Numbers 36:6-9)