Below is the chat I had w/support online, it seems it is a known issue w/some gamgertags, they are aware, and are working to correct this. :-(
trish: he is allowed to log in under his sister's profile, just not his
Antony: Yes then his gamertag has been affected by the localized outage that is currently going on.
trish: Any ETA when this will be resolved?
Antony: There is no estimated timeframe for a solution,but we truly are working diligently to resolve your issue. What I suggest that you do is to try to log into your profile/redownload it in 30 mins or an hour.