Albert Barnes Commentary Leviticus 18:12

"Thou shalt not uncover the nakedness of thy father`s sister: she is thy father`s near kinswoman." — Leviticus 18:12 (ASV)

Your father’s sister - The instance of Amram and Jochebed (Exodus 6:20) seems to show that marriage with an aunt was not considered wrong by the Israelites when they were in Egypt.