Long easy logic riddles for kids

I may seem real yet I am not, Once you're gone I'm often forgot. Time here stretches and it shrinks, It all depends on how you think. I may be good, I may be bad, I may be the same as one you've had. What am I?

There is a box full of marbles, all but two are blue, all but two are green, and all but two are red. How many marbles are in the box?

A man while looking at a photograph said, "Brothers and sisters have I none. That man's father is my father's son." Who was the person in the photograph?