My absentee father has reappeared in my life. Should I build a relationship with him?

He has been out of my life most of the time and now, he is writing me from prison. Is he writing me out of lonelyness or boredom? What should I do? He is asking for forgiveness and I do forgive him, but is it wise to have him in my life. I am happily married with kids and life is really good. Will this complicate my life? I don't know if I want my kids to meet him because he has yet to reveal why he is in prison. I'm kind of intrigued and want to have him answer questions.