Ok, Gordon Freeman and Gman are both androids, ladies and gentleman. Not space agents, government agents or God agents. They are artificial beings, created on earth (Aperture Science Laboratories).That's why they are similar to each other. There's nothing told about Gordon's past, he is an ordinary scientist but in the same time efficient killing machine. Everybody around (Breen, Gman) tells you about your employers, you have feeling they know something about you, that you don't know. You not grow old (beetween HL1 and HL2). Gman can immobilise you, because you're programmed the way THEY want and maybe you will be activated when the time comes(Bioshock anyone?). The thing i don't know is, if Gordon Freeman (as the peak of technology) was created to defend humanity from Combine because THEY knew Combine's coming or he was created for not so noble, darker purposes, or maybe both. Probably Black Mesa was just a final test for Gordon. Now add yourself couple Gman's hi-tech technologies from Aperture Science Laboratories: portal techonology and time control and you have pretty much all your questions answered. NOW. Who are THEY, those employers, sientists from Aperture Science Laboratories? Well, that will be probably answered in Episode 3, and will be most interesting part of HL series imho. Who knows, maybe even the head of this organization, government, whatever, is the man who borrow his face to Gman or Gordon) (remember Alien's Bishop?).