A.T. Robertson Commentary Acts 7:14

"And Joseph sent, and called to him Jacob his father, and all his kindred, threescore and fifteen souls." — Acts 7:14 (ASV)

Three-score and fifteen souls (εν ψυχαις εβδομηκοντα πεντε). Stephen follows the LXX which counts some grandchildren of Joseph and so makes it 75 whereas Ge 46:26 has 66 and then the next verse makes it 70 including Jacob and Joseph with his two sons. The use of εν means "consisting in."