My brother has an older model X-box 360 an Elite and is fully up to date but Dawnguard is not available to him? Is there something going on that makes Dawnguard available only for the newer x-box's?

Did he update his Xbox when it being request?

Got an xbox console that is still from launch date(yeah really)) and I have DG. Something else going on here...really strange.

Has he tried from the in game menu; add ons?

Yes to to both. It is really weird because I already have Dawnguard.

We were able to find it in the menu after checking again. Thanks for you're help guys.