The names of Jacob's sons
At first glance, the story of Jacob's sons feels like an obvious just-so story for the twelve tribes of Israel. Jacob AKA Israel has twelve sons and these are the twelve tribes. Except Joseph isn't a tribe, instead his two sons have a tribe each. And while Levi is Jacob's son, the Levites sit outside the twelve tribes.
It seems odd that someone wanting to invent an origin story for the twelve tribes and the Levites would make things so complicated. Why not invent that Jacob had thirteen sons, including Levi, Manasseh and Ephraim and forget about Joseph entirely?
Are there any authors who have suggested some pre-established traditions that place Joseph as Jacob's son and insist that he only had twelve sons? Or have there been any other interesting theories on this?