He is probably a narcissist and was keeping you around to continue using you, and or until he found another, and I heard some will be in private relationships but to others around them live a single life. You must have fulfilled a need he had, did he approach you during a hard time? End it during a hard time too? That is also typical Narcissistic behavior as well. I am sorry to say he might have continued so long just so you would always think about him, feel hurt. People like that take pride in knowing they might have destroyed another, it is weird but people are that way.
If it was myself, and in this situation I would contact whoever possible and rat him out. He won't expect it and it will throw him off his games, and even if he covers well, and continues to deceive his family you caught him off guard, and will realize his spell has been broken.
I am sure others will eventually weigh in and offer advice.
“The world would be a nicer place if everyone had the ability to love as unconditionally as a dog.”