I think it's still a new plan and that we haven't seen these kinds of questions posted in the forum previously.
So I would guess that the answer is "No one knows."
There seems to be some of those questions being asked on Reddit. You might try to ask there.
https://www.reddit.com/r/Chesscom/comments/1mdwaae/what_happens_when_the_owner_of_family_friends/

Hello everyone,
I’m posting here to ask about a situation that a family member is going through, in hopes that someone from the community or the support team can clarify.
Situation:
He had a family membership / plan on his main account.
Unfortunately, he was banned because he had two accounts (which is against the rules).
Chess.com support already restored a premium membership to his new account, but did not transfer the family plan yet.
He is waiting for the support team’s decision regarding the family membership.
Questions I’d like clarified:
Has anyone ever had a family plan transferred from a banned account to a new one?
Under Chess.com’s policies, is it allowed (or typical) for them to refund or reassign a family plan in such cases?
What kind of arguments or proofs helped people convince support to grant a transfer or refund?
If the support denies the transfer, is there any recourse (appeal, escalation) that has worked?
If you’ve experienced something similar, your insight would be very helpful. Thank you in advance!
Best regards,
softpumper