both parents w/schizophrenia/mental health issues?

Yeah, the predisposition means that he may be more likely to develop the disorder due to his genetic make up. Unfortunately, there are no hard and fast rules as to how much of it is genetically determined and how much of it is environmentally determined. I've seen people who have their first psychotic break and are from stable, upper class families and some with horribly unstable backgrounds. There are structural changes in the brains of those with schizophrenia, unfortunately it is uncertain if these structural changes are due to the illness or a by-product of it. The one thing that I will say is those with a supportive family tend to be higher functioning than those who don't.