If a biological father impregnated his daugther and they had the baby, who is the grand father?

This is a weird question but, this is provocativedebate.com site designed and operated for weirdness. We shine laser beam on issues and topics that others are not courageous enough to pose and post to the public. This is an incest to many of us but, things happen behind close doors in every society across the globe. When a father impregnated his biological and they had the baby, a very complex network of relationships is triggered. This man is the father of this baby and at the same time the biological grand father. His daughter is the biological mother and the baby is half sister or brother to her/his mother. If they were legally married, can they truly divorce? Do family members divorce each other? Weirdness shall never end. Welcome to provocativdebate.com, known for controversial debate questions.