In this connection, the Guardian feels the necessity of bringing to your
attention the fact that the validity of a Baha'i marriage is conditioned
upon the consent of the two parties and their parents only. So that in
case the other members of your family show any dislike or opposition to
your sister's union ... their objection does under no circumstances
invalidate it. Your parents' approval would be sufficient, even though all
the rest of your family may violently oppose it.