SPOILER in GOW2:

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.Well they braught the Barbarian King back for GOW2... its forceable they could or will bring the brother back. Although some things did seem out of place from those vidoes in GOW1. Like Kartos being surprised that Zeus was his father inGOW2 when his mother supposely already told him about it in GOW1, he even had to kill her for it. 

Well that game was supose to be a stand alone game... but since it made so much cash they said:"What the heck"... and decide to milk the series for more cash... of course they are miling it expert hands and not just Devil May Cry 2 miling hands (DMC2 was bad).  

I don´t know about future enemies, allies, betrayals or friendships... but some how it will end (I think) everybody dead or something... becuase Barlorg has stated that they want to explain in the game why it is that none or any major deity exists in present day.