These also are the generations of Aaron and Moses in the day that the Lord spake with Moses in Mount Sinai, that is, this is their further history at this point. Aaron is here named first, because his sons were the heirs of the priesthood.
Related Commentaries of Numbers 3:1
Numbers 3:1
1 These also are the generations of Aaron and Moses in the day that the LORD spake with Moses in mount Sinai.