So, when the DLC for Fallout 3 first came out, I bought BS, TP, and PL on one gamertag. i gave my brother some microsoft points for xmas and on his gamertag he ended up buying the last 2 DLC's, OA and MZ. I've recently tried playing Fallout 3 and on my account it doesn't register the ones he bought, and on his it doesn't register the ones i bought. This is all on the same Xbox. Is there something I need to do to get it to recognize it?

there are 2 ways to resolve this

Step 1: sign into his acct, start up fallout 3 and press start and let it load then sign out and sign into the account you want to play on and it should work

Step 2: go to xbox.com sign into his account and go to My xbox then accounts and register that account you want the dlc for and re download it