דברי הימים א, פרק כ״ה, פסוק י״ב

The organization of the singers in the Temple relied on a lottery system to assign their work shifts. This method ensured that the daily schedule was determined fairly and objectively, completely separate from a person's age or original place in the family tree.

Through this process, the fifth shift was assigned to Nethaniah. Although he was actually the third son of Asaph, he received the fifth position overall. This outcome highlights how the lottery randomly mixed the different families together and created a brand-new order for their service [רש״י]. To carry out the musical duties of this specific shift, Nethaniah was joined by his sons and his brothers, forming a dedicated group of exactly twelve men.