What does Genesis 46:26 mean?
The middle part of this chapter (Genesis 46:8–15) has listed all of Jacob's official descendants by each of his four wives. This and the following verse total up those numbers.According to this count, 66 total persons came with Jacob into Egypt. This number adds in Dinah, Jacob's daughter by Leah, who was left out of the count of Leah's offspring. It removes Er and Onan, who died in Canaan (Genesis 38:7, 9–10), and does not include Joseph or his two sons. The following verse will add back in Joseph, his two sons, and Jacob himself to the total count.
As stated clearly here, the count does not include the wives of Jacob's sons and grandsons. It is possible the count is meant to total up to 70 in the following verse, a number often representing a completed or finished group in the Old Testament (Exodus 24:9; Jeremiah 29:10; Daniel 9:24).