Honestly, whether or not marijuana is helpful for pain, if you are located in an area where it is illegal, your parents could lose custody and get into serious trouble for providing it to their child.
I am not sure that even in medically legal states it would be prescribed to someone under the age of 18?. Your parents would first need to consult your brother's physicians before using anything else in conjunction with the ketamine
In addition, there are studies that suggest that marijuana may induce schizophrenic symptoms in susceptible young people
We have an RSD forum here where you may find additional info on RSD/CRPS
http://neurotalk.psychcentral.com/forum21.html