Born of the Sea, Raised by the Sky

When Zeus finds out about Poseidon's 7-year-old son, he is furious. Reeling from the death of his daughter Thalia, Zeus prepares to strike the boy down with lightning - but falters when he sees two mortals arguing in the room opposite the boy. When he witnesses the woman's gruesome death, he kills the man who murdered her, and raises the boy as his own. AU Where Zeus raises Percy.