The twins first meeting with Professor Xavier was not intentional or peaceful.
Xavier was at his local bank investigating why his accounts had been frozen (apparently due to the Professors falling out with the Hellfire Club his accounts had come under investigation but this was only a ploy implemented by the Club to acquire his assets). The twins abruptly entered the bank arm with two automatic weapons demanding all the money. Due to their innate mutant ability the boys were able to destroy the security systems via an electromagnetic pulse. Xavier attempted to telepathically read their mind(s) but their conjoined brain proved very difficult to read. The bank was soon surrounded by police and the bank robbery became a hostage situation. Xavier used his telepathy to communicate to his fellow hostages in order convey a plan he had concocted. The plan led to Syndicate being overwhelmed by them, he then allowed everyone to go but Xavier stayed to help talk to the scared mutant. The boys weren't actually as villainous or greedy as they originally appeared, Syndicate revealed to Xavier they were only robbing the bank in order to acquire enough money to help pay for their sisters cancer treatments.
Xavier attempted reasoning with the boy using their sister as collateral. Due to their resistance to reasoning Xavier searched their mind to discover the location of their sick sister, he then threatened to mentally order their sister, Alice, to limp to the roof of the hospital she was in and jump to her death. This threat finally caused the boys to give in and offer to give themselves over to the authorities. Xavier instead offered another way out of their situation. He offered to pay for their sisters treatments and in order to "pay him back" the boys were to investigate the Hellfire Club in order to regain all his assets and once they had done that they could attend his school and learn to control their power. They agreed and Xavier telepathically led the police, former hostages and on-lookers to believe the twins were gunned down so there would be closure to the situation.
Quite sometime later, now living at the school, the boys joined Psylocke and a few others in defeating the Fenris twins. While attending the Xavier school the boys learned to temporarily disable the electromagnetic pulses their heart gave off.
Sadly, their career with their fellow mutants was cut short during Ultimatum. William Stryker led a raid of the school using salvaged sentinel technology found amongst the rubble of New York. Stryker and his team came upon Syndicate while the twins talked about missing their family, Syndicate was the first death in Stryker's massacre of the school.
The twin possessed a heart that gave off a powerful electromagnetic with every beat. Originally involuntary the boys did gain some control of their electromagnetic powers.
Due to the complexity of their conjoined brain and extra grey matter their mind provided a natural resistance to all forms of telepathy.