In Sefer Shmot, Parshat Va’Eira, Chapter 6, Pesukim 14 to 25, the Torah begins to outline the Genealogy of Klal Yisrael in Mitzrayim.
Why does the Torah only enumerate the first 3 Shvatim? What happened to the other Shvatim? Why for Shevet Levi does the Torah enumerate the 2nd generation and also the 3rd generation whereas there is no mention by the first two Shvatim? What happened to Hebron mentioned in Pasuk 18?
See Rashi on Posuk 14, who gives two answers to your question. The first is that since the torah is now going to talk about Moshe and Aharon. The torah wanted to make it clear who exactly they were, and their ancestry, see verse 26-27. It is for this reason that Levi is enumerated more, because that is where Moshe and Aharon came from. The other two shevatim are mentioned as derech eretz not to skip over them, since they essentially come first in order of their birth, therefore they were also mentioned. Rashi brings a second explanation, that these three shevatim were not given a specific blessing from Yackov, and in order that no one should think that they are illegitimate, therefore the torah specifically talks about them.