Ok. So what we know so far about these guys...

1 The guy is 27.
2 He comes from 23 years in the future and I suppose we can assume she as well.
3 He comes from another country.
4 23 years in the future is when Andrew dies when he shouldn't have.
5 As per a Devianart... art... Andrew knew Set in the "bad future" (they looked rather close... coughShipcough?)
6 This Set is from the future.
7 These two aren't the only ones. There's more. They probably all came from 23 years in the future. Apparently Chronos is the one who sent them back.(see next page)
8 They want to avoid Abaddon at all costs. (Too bad, she's already in the vicinity guys.)
9 The one who "killed" Andrew was Abaddon, "by mistake" 23 years in the future (2031 if it's 2008).
These guys want to avoid Abaddon and come from this time. Hum. Did Abaddon go on a rampage or something? And how does Chronos fit into this?
10 These guys know Set, but they don't know Andrew-from-the-future. He didn't change that much, yet they didn't recognize him.
So I guess Andrew could have been on Set's side and got himself killed by Abaddon, (and by "coincidence" she asked Set's bro to help Andrew. We already know there's more to Abby than the silly, loving mommy...) and they want to avoid the future when Andrew takes Set's side? Hmm.

Could it be that the war didn't happen yet and Andrew got killed during it?