Parents send their children to bed, and they have to listen to authority since they are dependents.

Who is "they" in this prior sentence?
their children
The ball broke the window because it was hard.

Who is "it" in this prior sentence?
The ball
Modern Warfare has big expectations to live up to due to the successful release of Battlefield 3 since they need to pull fans to their game instead.

Who is "they" in this prior sentence?
Modern Warfare