It is not uncommon for a person who believes they hear from YeHoVaH to rise up against and/or challenge the chosen leader YeHoVaH has called to lead. Moses was challenged by the Children of Israel on several occasions throughout Torah.
In the previous Chapter, Moses was challenged by the people of the community. In this Chapter, Moses is challenged by his own family members: Miriam, his sister who was a Prophetess, and his brother, Aaron, the High Priest chosen by God.
In preparation for the study, Know Your Place, please read Numbers 12:1-16.