Yes the boy was indeed dead. After reading it it is pretty easy to figure that perhaps he's stuck in limbo or purgatory, and he was waiting for his sister to come and get him. The angel and devil were obviously trying to persuade him to go to heaven or he'll with one of them.
the boy was near death or dead and was waiting for his sister who is also dead to come and get him.
He is dead and his soul return to heaven with his sister
i got that he was dead from the start , but i was surprised that the black one was the angel and the white the devil=P
I liked the ending but in the end I wish I could read more. (thought i don't know id that boy was dead or not)