I don't see this as a contradiction to the parent. Those things you listed to prove your point can all happen to any of us at age 12, and all of the rest save

I don't see this as a contradiction to the parent. Those things you listed to prove your point can all happen to any of us at age 12, and all of the rest save child-bearing can happen at any age. All of them are external things that change our situation, sure, but your choice to be "old" or not based on them is still a choice, which was the parent's point.