Conversations with a 4 year old

We're sitting at the dinner table together (this and the car seem to be the best recipe for good conversation) when my son looks and me and says

B: Mom, am I a brother?
Me: No honey, you aren't a brother
B: Why not?
Me: Because you have to have a brother or sister to be a brother
B: Why don't I have a brother or sister?
Me: Well, daddy and I have only been blessed with one child so far and you are it
B: Well, I want to be a brother, can we get a brother or sister?
Me: We would love to have another baby but I just don't know if we will or
B: Oh, I don't want a baby
Me: What do you want?
B: I want a boy or girl like me so we can play, babies can't play
Me: Well, I guess we'll just have to see what happens
B: Okay, well I guess we'll just have to get a dog then

Well, why didn't I think of that..LOL But seriously, it's the first time he has realized that he is a only child. It kind of breaks my heart because I've always wanted to have more children. I grew up thinking that I would someday be a mommy and I would have 4 children. It turns out that I am not entirely in control of these things (imagine my surprise) We were blessed to have Blake just drop out of the heavens to us. I don't think lightning will strike twice and I'm almost 36 so when will I just get over it and realize that this just might be it. I hope that he doesn't grow up feeling somewhat slighted that he is the only one. We'll just have to see what happens next and if nothing else. We have two furry children called Max and Cleo (our cats) and maybe we'll just have to get that dog. I hear they are like having another child anyway.