1. How are you going to feel in 20 years when John is in a nursing home? You go to see him and people ask if he is your dad, and you say it's your husband?
2. If you have a child, John will be in his 70s, when the child graduates high school. People will say, is that your grandfather? He'll say, no, that's my dad! Meanwhile, you'll be in your 40s.