Exodus 6:23

6:23 Aaron married Elisheba, the daughter of Amminadab and sister of Nahshon, and she bore him Nadab and Abihu, Eleazar and Ithamar.

Exodus 6:25

6:25 Now Eleazar son of Aaron married one of the daughters of Putiel and she bore him Phinehas.

These are the heads of the fathers’ households of Levi according to their clans.