" Ok, so im going to say it right know, and honestly everyone should know this, but you fight and kill hades in this game. Not shocking. But when you do fight him, you eventually rip his helmet off to reveal his actual face, and he looks very much like Cronos, his father. Atleast, I assume its his father because zeus is his brother, and Zeus's father was Cronos. Now, assuming that Im correct in thinking both hades's and zues's father is Cronos, I began to wonder why Hades was the only brother to really look like Cronos, when Zeus just looks more Normal and human. Then I remembered from GOW 2 that Cronos inpregnated a mortal women, and thus zeus was born. I assume this is why Zeus looks different and more human then Hades does (im talking facial features, not the fact that hades in red and has spikes coming out of him. His (hades) facial features are pretty much a dead ringer to Cronos) But then, how was hades born?   Anyway, im not majorily knowledgable in Greek Myth, so if someone knows, please let me know. "

Things like that are sometimes not born, but crafted. Kind of. 
@SathingtonWaltz said:

" @Raven_Sword: It's probably one of the many mythological plot holes apparent in every religion ever. Kind of like how in the book of Genesis, when Cain is exiled, they never explain where the city he found came from. "

Actually, Rhea wasn't a mortal woman. She was a titan, but she has the same appearance as a mortal woman in GoW2.

" Actually, Rhea wasn't a mortal woman. She was a titan, but she has the same appearance as a mortal woman in GoW2. "

i don't know a lot about Greek myth, but i think titans where not big monster and thy can change forms anyway they where just very strong and wise people or something, but hades mother was another titan . 
 
if i remember correctly form my high school books , titans are portrayed like normal people on the old Greek sculptures, the titan= giant relation is more wester and modern i believe, but anyway, yeah Zeus and Hades are just half brothers.