The game's creator, David Jaffe, has said on many instances that 'God of War' will be a series of games and that a number of sequels will be made. Within the game there are special challenges that the player can take part in. If they win, they can unlock three bonus features. Each one tells of another story that is linked to God of War, leading most to believe that these stories will be the three sequels, and that one might even be a prequel. These are those stories.
As for Kratos's brother, he had died some time ago while he was still a young child living in the mountains. While he was coming to age living in the underworld, he thought of only one thing: revenge against his brother that abandoned him so long ago.
Although Kratos became the new God of War, killed Ares, and avenged his family, he was not satisifed. He never knew his father as a child, and his mother never told him who he was. Now as a full grown adult, Kratos went back to Sparta to ask his mother. When he arrived, his mother didn't have much life left in her. He demanded to know who his father was. As she was about to tell him, she was turned mysteriously into a wicked monster. Putting his love for his mother aside, he stabbed the beast. Before his mother passed away, she revealed the name of his father. It was none other than Zeus, king of Olympus. He swore revenge on Zeus for abandoning him and his mother.
What became of Kronos? Well, after a thousand years of wondering in the desert he died, and was covered with sand, but the mountain on his back remained. Then a thousand more years later, the mountain with Pandora's Temple within it was discovered by man who have come a long way since the time of ancient Greece. Upon learning of this discovery, one man fells a strange calling to the temple. He is not quite sure why or how or what he will discover, but all he knows is that he must go there.