The Torah says Joseph told his steward to "slaughter an animal and prepare" a meal for his brothers. Targum Pseudo-Jonathan hears more than catering. It hears halacha.
"Bring the men into the house," Joseph tells Menasheh, whom he has made superintendent, "and unloose the house of slaughter, and take out the sinew that shrank, and prepare meat before them" (Genesis 43:16). Gid ha-nasheh — the displaced sinew, the sciatic nerve — is the piece of the animal forbidden to the children of Israel after the angel wounded Jacob at the ford of the Yabbok (Genesis 32:32).
Joseph, raised by his father until age seventeen, knows this law. Even in Egypt, where he rules as vizier and could have anyone prepare anything, he insists that his brothers' meal be slaughtered properly and the forbidden sinew removed before the meat is cooked. He does not reveal himself yet. He does not say, I am your brother, I too keep your customs. He just orders a kosher kitchen into existence.
The Targum also names the steward Menasheh — Joseph's own son, still a boy, now serving as the house overseer. Imagine that detail. The grandchild Jacob has never met is quietly preparing the feast. Joseph is building, in the palace of Egypt, a miniature Jewish household where the laws his father taught him are still observed.
It is a hidden loyalty. The brothers will not understand it until later. But Joseph has already chosen, long before the reunion, which tradition will govern his table.