So this is a work around that seems to work 100% of the time. Trust me when I say I have tried EVERYTHING else! 1. Both players load the game and go to the tower. 2. Both player at the same time press the XBOX button and quit the game. 3. Both players at the same time start destiny again and this should generate a 'WEASEL' error. Thus shoukd usually happen to both players. 4. Close the error and continue to selecting your characters. 5. You should now be able to join the same fireteam team. I know it's a ball ache it this does genuinely work. You can even leave the fireteam after and you will have no issues rejoining. This is a fix for as long as you are online but the next time you play you will have to do this again. Just goes to show that this is truly a bungie issue as to get this to work no changes to any network settings need to happen. Hope this helps.