Answer:
Well, Some of the X-Men were unwanted and their parents (or guardians) chucked them out. In Bobby's case, his parents didn't know he was a Mutant, in X-Men 1 they thought he went to a Prep school. But, in X-Men 2 they find out that he is a mutant. BUT in Jeans case, her parents knew that she was mutant and Xavier wanted her to go to his school for the gifted but Jean thought he couldn't help her. Anyway in Wolverine's case (Logan) he killed his father and out of pure stupidity and scared he left with his brother and ran (starting credits to X-Men: Origins). Hope this helps.