Problem with my principal account

i'm having the same problem only on my principal account since the 28th november.. my brothers account don't have this problem why and what can i do??

You only have to put in the console B or C the account A as principal and so that the other one that was left without the account A as principal can take advantage of the resources only must have the session initiated of the account A.
Besides that there will be no problems when playing together between A and B but if they want to play A and C then they will not be able to do it since C does not have the account of A as principal.

Put your account as principal in the new console so your child can play without problems

1) Oh, maybe that's the problem.

2) It's the same Xbox and I checked the two accounts and both says Xbox Home (Xbox Principal).

Thanks for answer my questions.

Erm... you're saying the principal reason is licences. I'm saying it wouldn't be that. It is likely the
principal reason for this is using a different account.

It's likely licences will have to be transferred afterwards, provided that turns out to be the reason, but the initial problem needs to be solved before going down that route.