Q. If many menorahs are placed on one table, as when someone has a large family, does each menorah require its own shamash?

A. Mishna Berura (673: 18) quotes Mogen Avrohom ruling that since each one places his lights in a distinct place each one requires its own shamash.

Horav Shlomo Miller’s Shlit”a opinion is that if they are close to each other, in case of need, one shamash could suffice for multiple menorahs

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a