Prophet Yūsuf: Part 1 — The Well, the House and the Prison
Section 16 of 31 · Lives of the Prophets
How Old Was Yūsuf?
Yūsuf (peace be upon him) grew up in the house of al-ʿAzīz. One of the Islamic scholars estimates that Yūsuf was about fourteen years old when he was adopted, because when they took him out of the well they called him a ghulām, and that is usually the age of a ghulām; older than that is called a fatā. And he says that balagha ashuddahu — he reached his full strength — would mean twenty-five years old, even though there is a difference of opinion about what that phrase means.
We can estimate that the wife of al-ʿAzīz was about forty years old at that time. If they adopted Yūsuf when he was fourteen, let us say she was perhaps thirty then, because her husband was already al-ʿAzīz, and to have a position of that status usually takes some years. So by the time Yūsuf had grown up to twenty-five, she might have been about forty.