depresson in 9 year old boy

My friends so is 9 years old his pearents devorced when he was 4 and have since remarried and had kids his mum has a 4yr old girl his dad has 2 boys under the age of 4 with one on the way .He travils between houses on     wednessdays and gose to church on sundays with his Dad and family who also have him every other weekend .His Mums house she works as dose her husband and the kids go to day care .His Dads family his dad works and his wife stays home .He has always been bullied at school .Latly he seems depressed and says things like i can't do anything right I'am no good at anything .For e.g his mum droped him at school on her day off and saw that his class had made mosic vases and she asked which was his he said just look for the worsed on and thats mine ,They also went shopping and looked for a new quilt for his mum he chose one and she didn't like it but his sister chose one and his mum said it was o.k his said see i can't even do that right you liked hers best she always dose things better than me .When i suggested to his mum to take him out by himself  she said he dosn't apprecate it and only acts worse when they get home and when she trys to praise him up he takes no notice of it .He still wets the bed occasionly which he has treatment for and is constantly forgeting things he needs for school so that his mum has to be called  .
is he depressed or is it jelosey and how can we help him my fear is that he will become a depressed teen .