Predisposition to Grade IV GBM and Demyelinating Polyneuropathy

[sleepyinsomniac]

I have 3 older brothers.  My closest brother, 15 months older, has Grade IV GBM just diagnosed in April of 2009.  Good health; solid family; good income; good life decisions.... all is well.... then WHAM.  Two surgeries and one clinical trial later, we are still comprehending what is going on.  Prior to this, he prided himself on only taking one multi-vitamin tablet each day.  WHILE, I, on the other hand, am embarrassed to say how many meds I am on because I have been living with chronic idiopathic demyelinating polyneuropathy, fibromyalgia, restless legs syndrome, and sleep apnea for 6 years.  I am 55 and on social security disability.  MY QUESTION(S).  1.  Are neurological disorders, if not environmental or due to a specific underlying illness, more likely to be genetic than random?  If not, then the incidence of neurological problems between siblings would be purely coincidental?  3.  Could any of my illness be due to my Mother taking DES when she was pregnant with me?  4.  Could my brother's tumor be caused by ANYTHING from home?  Fertilizer, the heat, a severe fall, trauma during birth, the reason why he was 18 months before he walked, the reason why he was so brilliant in mathematics?  My father was an alcoholic, more so when my Mother would have conceived my brother and I.......  any similarities or research on the toxidity of sperm due to alcohol?  I'm trying to draw a parallel, something, anything that would shed some light on why we both have neurological issues.......  or is GBM considered cancer of the brain versus neurological?  Thank you for your help.