(3) Where any person who, if not under a disability, might have made any application, done any act or been a party to any proceeding under this Act or under any rules made thereunder is a minor, a person of unsound mind or a person under any other disability, the curator or tutor of such person, or if there is no such curator or tutor a person appointed under some written law to represent that person, may make any application, do any act and be party to any proceeding on behalf of that person, and shall generally represent that person for the purpose of this Act.