Judah sees a caravan of Ishmaelites coming from Gilead — their camels carrying spices, balm, and myrrh to Egypt. He speaks: "What profit is there if we kill our brother and cover his blood?" (Gen 37:26). Sell him. He is our flesh. The brothers agree. Joseph is pulled up from the pit and sold for twenty pieces of silver to the Ishmaelites. They bring him to Egypt.
The Ishmaelites are the sons of Ishmael — Abraham's firstborn. Joseph is a son of Isaac's line. They are cousins. The irony is deep: the Ishmaelites who carry the great-nephew of Ishmael down to Egypt are themselves the seed of the man cast out so Isaac could inherit the covenant. Now Isaac's covenant seed is carried down in their hands. The two lines of Abraham are joined in this transaction.