PROVIDENCE, R.I. — A memoir by former Congressman Patrick Kennedy has created a rift with family members upset over his portrayal of family secrecy, substance abuse and mental illness, including of his father, late Massachusetts Sen. Edward Kennedy. Kennedy on Tuesday defended his book, “A Common Struggle: A Personal Journey Through the Past And Future of Mental Illness and Addiction.” He said he loves his family but that he feels it is important for him to talk openly about the mental illness and addiction he and relatives have suffered. “My family does not want to be identified with a medical illness.