To a Levite he held the priesthood. It was called the Levitical Priesthood or order. Aaron had the higher order.. Not two priesthoods, just one priesthood two orders.
Correction please, Moses held the highest order, for the redeemed congregation of Israel, chosen by GOD HIMSELF personally to be the mouth for HIM, even while Moses was alive. Moses remain by the will of GOD for the congregation in the desert as a leader, a teacher, a prophet, a judge and a great high priest. Only Moses was allowed to enter the Most Holy Place in the Tabernacle and the only one allowed to have communion with GOD, in order to address through Aaron to GOD's redeemed people, establishing and implementing all divine requirements.
The order of Levi priesthood goes like this;
1. Great High Priest (Moses)
2. Head of Priest (Aaron)
3. Priests (Aaron's sons)
4. Tabernacle/Temple helpers (chosen Levis)
Aaron was chosen in order to help/assist Moses (to be Moses's mouth), from the beginning as spokesman for Moses serving the congregation of Israel in addressing all of GOD's requirements. And later also help in service to all the Tabernacle matters, being as the head of all Levi priests and helpers.
