From the article it sounds like he got his brother to sign, reading slightly between the lines. So his brother would be the one on the hook, legally, if that were the case.

A contract signed by a minor is voidable (can be cancelled without penalty) by the minor, but is not void (legally inoperable as if it never existed).

HOWEVER, if a contract is cancelled, both sides must return anything they received the other side party to the contract.