One might ask since Joseph had 2 sons, Ephraim and Manasseh, and Manasseh is listed having 12,000, just who is included in the 12,000 of Joseph in Revelation 7 if it is not Ephraim?
Just an observation.
Joseph takes the place of the name of Ephraim.
Thus, the tribe that came from Joseph (Ephraim) returns to him because of Ephraim's sin (Hosea 4:17)