This document is about Mahli (son of Mushi). For other homonyms, please refer to the Mahli document.
He is the son of Mushi, son of Merari. In other words, he is Merari's grandson. For reference, there is also a namesake, Mahli (son of Merari), who is Merari's son.
1 Chr 6:47Shemel was the son of Mahli, Mahli was the son of Mushi, Mushi was the son of Merari, Merari was the son of Levi.
In other places, he is recorded as Mahli (son of Mushi). See link for reference.