sameSame thing happened to my Clash of Clans account. My friend and I had same game centerGame Center, changed Game Center but the data was still stuck in Ipadon his iPad so he couldstill had access to my game on his IpadiPad and Game Center. II would delete all of the info from your brother's IpadiPad and then redownloadre-download it maybe. And you guess can't be on at the sane time.