In Exodus 4:20 (NASB)
So Moses took his wife and his sons and mounted them on a donkey, and returned to the land of Egypt. Moses also took the staff of God in his hand.
and in Exodus 18:2-5 (NASB)
2 And Jethro, Moses’ father-in-law, took in Moses’ wife Zipporah, after he had sent her away, 3 and her two sons, one of whom was named Gershom, for Moses said, “I have been a stranger in a foreign land.” 4 And the other was named Eliezer, for he said, “The God of my father was my help, and saved me from the sword of Pharaoh.” 5 Then Jethro, Moses’ father-in-law, came with his sons and his wife to Moses in the wilderness where he was camped, at the mountain of God.
I presume Moses's wife and his sons never made it to Egypt or left at some point?