How come I do not have too...

Again, I got back from work and found out that Gwenchik was not behaving her best with her grandmother. I explained that I only have one mom, and Gwenchik has to take care of her, treasure her and listen to every word she says and do her best not to upset her...

Gwen: I understand. You know, when you get really, really old, I will also take care of you.

Me: I hope so.

Gwen: But you have two fathers, so if one gets upset you always have another one. How come I do not have that? I only have one Dad...

.....

What do you say to that?