Greg adopt a kid? That's a little farfetched, even for Greg. He doesn't even have a steady girlfriend, so why would he want to be tied down with a child? I just can't see it at this time. Perhaps one day in the future when he finally settles down with one woman to love, but of course we'll never see that because the show will be cancelled before that ever happens. I can, however, see Greg tutoring kids in math, physics and chemistry. He'd be an outstanding part-time teacher. Kids would love him because he can relate to them on their level.
I've always considered Greg to be sort of a mini-Grissom...only not secretive, but very open and friendly. One of the things I admire about Greg is that he's not afraid to let his superiors know what he's thinking. He's not shy about telling someone his ideas or theories, and I think that Grissom respects him for that. Whereas we have sycophant, butt-kisser Hodges fawning all over Grissom and other higher ups, Greg just lays it all on the line, whether they like it or not. And his intelligence generally backs up his theories.