I'm sure I'm not the first person to have noticed this, but the stories for both Rage and Brink, even though they take place in drastically different settings, seem really similar.  The most striking parallel is the "ark." In Rage, arks are underground shelters for the world's most capable people, while in Brink, the ark is a city in space that acts as a refuge from  troubled planet Earth. 
 
Then there's the whole "the fate of the world is in your hands" thing. In Rage, you scout through the desert and wipe out tribes who have seemingly taken over Earth while you search for the other arks. In Brink, you're responsible for the future of humanity as unrest has been brought among the refugees on the ark  (well, that's the gist of what I got from Paul Wedgwood's Bethesda blog).
 
This isn't particularly surprising since both games are being developed under the same parent company (except that Splash Damage doesn't belong to ZeniMax, though Bethesda is working in partnership with them on Brink). But I still find it kind of... odd. Is this intentional? Have I missed something?

no, it's just that post-apoc games are ridiculously popular nowadays, "ark" is a biblical reference that both games drew upon, and the fact that they share publishers is coincidental.