Yes, MEMBERS is a Scrabble word!

Letter values in Scrabble US: M 3, E 1, M 3, B 3, E 1, R 1, S 1.

Is it a valid word?

MEMBERS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

one of the persons who compose a social group (especially individuals who have joined and participate in a group organization)
anything that belongs to a set or class
an external body part that projects from the body
an organization that is a member of another organization (especially a state that belongs to a group of nations)
the male organ of copulation (`member' is a euphemism)

Also: fellow member.