It says in Sota 11b that the houses which were given to Yocheved and Miriam are interpreted as kingship, and the gemarah says that Dovid comes from Miriam. I'd like to know how that is possible given that Miriam married Calev and Dovid's ancestry is pretty clearly not from that line on either side. In Divrei haYamim I chapters 2 and 4 it shows unequivocally that Dovid comes from Ram, Calev's brother.
1Was inter-shevet marriage not common?– Noach MiFrankfurtMay 9, 2014 at 13:36
@Noach In the desert it was forbidden– Double AA ♦May 9, 2014 at 16:47
@DoubleAA, would their descendants need to have married in the desert, seeing how Shevet Levi seems to have been mainly concentrated in Yehuda, it would not be surprising if there were a relationship within the intervening hundred-odd years.– Noach MiFrankfurtMay 9, 2014 at 18:23
Peretz, Chetzron, Ram, Aminadav, Nachshon, Salmon, Boaz, Oved, Yishai, Dovid.
Nachshon was the nasi of Yehudah at the time of the Exodus.
Sotah 11b says that Dovid descended from Miriam. However, Calev is not mentioned. Some commentators connect Dovid being called Efrati with Miriam (Efrat) and say that one of her descendants married into the family (possibly a wife of Nachshon, Salmon, Oved, or Yishai)
As an example, Illegitimate Origins of King David's Dynasty
The Talmud says (Sotah 11b) that because Miriam aided her mother Jochebed in saving the Jewish babies in Egypt, Miriam merited that King David's dynasty should descend from her. The proves that Miriam was a foremother to King David by explaining that Miriam is called Efrat, after Caleb nursed her back to health following her deadly illness, and King David is known as an Efrati. Rabbi Shmuel Eliezer Eidels (1555-1631) asks that the lineage of King David is traced in the end of the book of Ruth (as mentioned above), yet neither Miriam nor her husband Caleb are listed as being ancestors of King David. Rabbi Eidels offers the possibility that Ram son of Chetzron, a great-grandson of Judah, was the same person as Caleb. However, he disproves such a possibility because Caleb was actually a brother of Ram, as is evident from Chronicles 1 2:9 which lists Yerachmiel, Ram, and Caleb–referred to there as "Celuv"—as the sons of Chetzron. Rabbi Eidels assumes that the Caleb referred to in that verse is identical with the Caleb who married Miriam, however this assumption is debatable, and so it is possible according to some explanations that Ram indeed is identical with Caleb and "Celuv" mentioned in the above-cited verse is another person. Rabbi Eidels concludes that since the family of Elimelech (the father of Machlon) is also called Efrati, it must be that Ram or one of his descendants (Aminadav or Nachshon) married a female descendant of Miriam and Caleb and the resulting offspring fathered the Davidic Dynasty.
To add to your point about Nachshon, the Midrash Shocher Tov 18:27 says that Dovid came from the seed of Nachshon.– DovAug 11, 2020 at 10:13