The sons of Aaron were Nadab the first-born, Abihu, Eleazar, and Ithamar

Nadab and Abihu died in the LORD's presence when they offered unauthorized fire before him in the Sinai wilderness. Since they didn't have their own children, Eleazar and Ithamar ministered as priests under the authority of Aaron their father.

This is the work of the tribes of Gershon at the Tent of Meeting their duties under the supervision of Ithamar, the son of Aaron the priest.

This is the work of the tribes of the descendants of Merari with reference to their service at the Tent of Meeting under the supervision of Aaron the priest's son Ithamar."

To Aaron were born Nadab, Abihu, Eleazar, and Ithamar.