Third time's the charm?

I write this knowing that it may not reflect the new millenium sensitivity that we are meant to display towards any type of difference, but heck.

In a later chapter of Nick Hornby's delightful book, he references a book about autism written by the mother of two autistic sons. The author also has a third son who does not have autism, which presumably makes for a nice change. The thing that I find absolutely flabbergasting though is that the boy without autism is the youngest of the boys.

What?

1. First of all, if you already have two autistic sons, how do you imagine you will have the energy to raise a third child at all? How would you have the energy to have even, say, a goldfish?

2. If your first son was autistic you might perhaps think, "We love him, of course, but this is not entirely what we imagined. Let us have another child who may let us fulfill our original vision of parenting." Fine. I can see this. But when your second child is also autistic do you really roll your genetic dice again?

I am baffled by this. And yes, I am a terrible, heartless person. Obviously.