If they've registered an email address, they can use it to log in.
If they haven't registered an email address and would like to use the same account, please contact us using the Inquiries button here and include relevant account information. We'll do our best to help!
(Please note that there may be cases where it is not possible to restore account access.)
Another option is for an Album Admin (parent member) to re-invite them by going to the Settings tab and tapping "+ Invite Family" below the Family Members list.
They'll be able to register a new account from the invitation they receive.