When I read Paul's writings, he used the word 'member' in a very different way to what we do.
Membership, for us, is all about entitlement. I pay a fee, I carry a card, I get access. I'm entitled to be a part of this community.
Paul used "member" in the context of a body metaphor. The member of a body is an extension of that body - it assumes belonging and participation as a part of that body.
I belong to a community, and I participate in a community as an extension of that community.
Not as my transaction for entitlement.
1 Corinthians 12:7-31