Is there a way to only allow a single account to play games digitally purchased on an xbox one?

I share an xbox with my little nephew. We both have our games digitally downloaded on it. All gamertags on the xbox can play any digital game. I recently saw him playing my GTA game. I'd rather he waited until he was older than eight to play it, so I'd like to restrict access to digital games purchased with my gamertag to my gamertag only. Is there any way to do this? Any other ideas on how to stop him from accessing certain games? He's probably crafty enough to disable any family setting unless they're password protected. Thanks.