Brian Banner becomes convinced Bruce is a mutant
Life, Failure / Mishap
After witnessing his son solve a puzzle he had been given for his birthday unusually quickly, Brian Banner, who had been suffering from increasingly strong paranoid delusions for several years, became convinced that Bruce was unnatural. Specifically he believed that Brian's exposure to radiation while working at a nuclear research facility had caused his son to be born mutated.
This belief caused him to become cold, and eventually violent, to his son, and to his wife when she tried to persuade him out of the belief.