Maybe because they're ours. Maybe because they represent our hopes and dreams. Maybe its the fact that we have some innate instinct to protect them at any cost.

GP - I figure you don't have any kids of your own, but perhaps you have a younger brother or sister, or perhaps you're an uncle. If so, wouldn't you run into a burning building, without thinking of your own safety, to save one of these kids? If some madman started shooting up the street, wouldn't you block the kid from the bullets with your own body?

In short, its called "love".