Pip returns to Joe and Biddy after many years. What has happened since he last same them and why is Biddy so insistent that Pip get married?

Biddy and Joe have a baby. The kid looks like Pip. Pip wants to hang with the baby but Biddy insists Pip get married. She mentions Estella and Pip gets all weepy. Pip insists his heart has already been ripped out and used as a trampoline.