While explaining the purpose of his small plates, Nephi implies he is putting Lehi's lineage in his other plates:
1 And now I, Nephi, do not give the genealogy of my fathers in this part of my record; neither at any time shall I give it after upon these plates which I am writing; for it is given in the record which has been kept by my father; wherefore, I do not write it in this work.
2 For it sufficeth me to say that we are descendants of Joseph. (1 Nephi 6)
This is subtly confirmed as Mormon abridges the large plates of Nephi and knows more detail about the lineage of Lehi:
3 And Aminadi was a descendant of Nephi, who was the son of Lehi, who came out of the land of Jerusalem, who was a descendant of Manasseh, who was the son of Joseph who was sold into Egypt by the hands of his brethren. (Alma 10)