Sound like double trouble? Over-employment? The latest synagogue sitcom? Probably; but Jewish history is never probable.
We started that way. Moses could not, would not, lead alone; Aaron had to be there. Moses' older brother never was quite his associate rabbi. Aaron was vastly more popular. He was the nice guy: arbitrator in congregants' business disputes, mediator in spousal clashes, peacemaker in sisterly spats, and conciliator for anyone with a teenager at home. Mr. Nice.
Moshe was more the patrician than the paternal. The teacher, not the counselor; the lawgiver, not the therapist. Mr. (sorry relativists and wannabe brides) Right.
Moshe embodied truth; Aaron embraced peace. Truth demands integrity; peace requires compromise. Torah insists on both, hence a team was needed for the making of a people – not an individual.
Moshe rarely enjoyed public support; his method, leadership qualifications, and integrity were regularly challenged, and accusations of nepotism drained him. Aaron was rarely taken to task, and then only because of his association with you-know-who.
The brothers' dichotomy did not abate with their deaths; the turnout at Aaron's funeral nearly doubled Moshe's. Not surprisingly, it was only upon Moshe's passing that despair threatened the people. But while Aaron's popularity earned him a larger funeral, Moshe's instruction earned him the role of leader. Aaron's passing evoked mourning; Moshe's passing created a terrifying void. Like money, you appreciate leadership when you don't have it.