How did you decide on age groups?

We have young bio kids in our house, so we had to keep their safety in mind. But if you don't have other children in the home, I think this decision is best based on the age kids that you feel most at home with. Whose company do you enjoy the most? And talk to your husband about how he'd feel if you get a 13 or 14 year old boy who hates sports and is a total book worn science guy? Will he still be able to find a way to relate to that child and cherish him for who he is?