What are laws with siblings sharing a bank account and one takes all the money out but the other was who the money belonged too?

one of the problems with a joint bank account is everyone on the account has access to all the funds in the account. this also applies to overdrawn balances, if an account has a negative balance then all signers on the account can face the negative consequences. on the other hand if only one of the siblings in question is a signer on the account that person would have legal right to all the money in the account.