Jamieson, Fausset and Brown on Genesis 46:8-27

8-27. all the souls of the house of Jacob, which came into Egypt, were threescore and ten--Strictly speaking, there were only sixty-six went to Egypt; but to these add Joseph and his two sons, and Jacob the head of the clan, and the whole number amounts to seventy. In the speech of Stephen (Ac 7:14) the number is stated to be seventy-five; but as that estimate includes five sons of Ephraim and Manasseh (1Ch 7:14-20), born in Egypt, the two accounts coincide.