From the BAR by-laws:
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Article II-Membership
Section A
Any person, or persons who have an interest in marine knowledge and husbandry shall be eligible for membership. [...]
Section B
Membership shall not be transferable, and both membership and rights to the enjoyment of property of the organization shall cease and terminate upon death, withdrawal, expulsion or other termination of membership in the organization.
Section C
There shall be two (2) classes of membership.
Individual Membership is defined as a single individual.
1. Individual Membership shall cost $20 per year.
2. Individual members shall have one (1) vote in BAR general elections.
Section D
Family Membership is defined as any group of individuals residing at the same address.
1. Family Membership shall cost $30 per year.
2. A Family Membership shall have two (2) votes in BAR general elections.
Section E
The Board of Directors may change membership fees.
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So basically the family membership gets you a discount over individual memberships for interested parties that reside at the same address.
The family members collectively are treated as 2 members as far as voting.
We follow through on that general idea with regard to club events.
So in the case of the frag swap for example, 4 people under a family membership would get to participate as 2 individual members. 2 of the 4 would bring their frags etc and participate as 2 individuals.