Okay, so, to clear up some confusion, so to speak, when it comes to Ethan. He's not a kid of the Petrellis and Grays, so don't worry XD Not another one of those.
Ethan is from an AU Heroes 'verse, and is Peter Petrelli's twin. He was born three minutes after Peter, and unlike his brother, he has the ability to shut off powers, not absorb them; he's a power negator. He's a bit strange, kind of morbid type who tends to bury his emotions more than express them the way Peter does, and works as a mortician. His canon goes off from the events of the first season at Kirby Plaza. When Nathan flew Peter up into the air, after a while Nathan let go and flew to safety, suffering minor burns. Peter exploded as predicted, in the air, but he was unable to pull himself back in, and the sudden, massive expulsion of energy killed him.
At that point Ethan left. His history is still being worked out in the later stages, but at some point he joined Sylar and took the last name Gray, legally making himself Ethan Gray.
Sorry for any confusion.