Complex sentence: The telepathic leader and founder of the X-Men and a close friend of Erik Lensherr until their differing views of mutantkind's place in humanity create a schism between them.
Split into simpler sentences: The telepathic leader and founder of the X-Men. He is a close friend of Erik Lensherr until their differing views of mutantkind's place in humanity create a schism between them.