Quirks, Queries and Commentary—Genesis 41-50
Joseph was sold to the Ishmaelites sometime after his seventeenth birthday. (37:2) By the time he was thirty, he was in charge of Egypt. (41:46) Reuben would have been 36 or 37 years old (being no more than six and a half years older than Jacob).
Joseph had told Pharaoh that there would be seven years of good crops, followed by seven years of famine. So when his brothers came to Egypt, Joseph probably would have been 38, supposing his brothers came about one year into the famine. When they came for their second visit, and Joseph revealed himself to them, there were only five more years of famine remaining. (45:6) Jacob was 130 years old (47:9), and Isaac had been dead for ten years.
Joseph had been in charge of Egypt for nine years and sold into slavery no more than thirteen years previously, so Isaac was still living when he was taken from his family. It’s quite possible that he never lived at Mamre, near Hebron (the Bible narrative makes it sound as though Isaac died shortly after Jacob’s arrival at Mamre). If this is true, Benjamin was quite possibly only a baby when Joseph last saw him. Yet by the time he arrived in Egypt, he had ten of his own sons? (46:21)
Joseph was no older 39 or 40 when Jacob moved to Egypt (thirty when he took charge and the move took place in the second or third year of famine—depending on how long it took them to pack up and leave Mamre). Jacob was 130. Joseph was born the fourteenth year Jacob had been with Laban. 130 – 40 = 90. 90 – 14 = 76. Jacob was 75 or 76 years old (how long did it take him to travel to Haran where Laban lived?) when he received his father’s blessing and ran away from home? He was no young man as we imagine when we read or hear his story.
Joseph died before his brothers (50:24) at the age of 110. He had governed Egypt for eighty years.
I love doing these sorts of calculations because it gives a better picture for the stories. Yes, there are some problems, like Benjamin’s age when he moved to Egypt, but I am confident that there is an explanation for them. I’ve noticed that sometimes the Bible narrative is not always in sequential order and information is left out. Perhaps the listing of Benjamin’s sons was a listing of all the sons he had before and after moving to Egypt and were named at this point in the story because all Jacob’s grandsons were listed. It sounds like they were born before the move but maybe they weren’t.