I am 4 of 4 children (3 older brothers, the only girl) Hubby has one older brother. His father is an only child, and becasue of this we have decided we can't have just one (even though we are perfectly happy with the one we have.)
My advice in planning how many children to have is, have one see how it goes, how you feel and how your wife handles pregnancy and childbrith. Then when and if you feel ready, see about having another. After that see how you feel, stop there, or have another. I am not a big fan of having many kids close together. I think it has it's benifits later when the kids are older, but just way to hard on both the parents and the kids when they are young.
Little PhD (our 1st) will be 3 in the end of March. If all goes well we will have a second child Aug 2004. Personally I am thinking 2 pregnancys is enough for me, I am a wimp. However I am not 100 % sure I want to be done having kids after this one, so who knows? However hubby is ready to go under the knife when number 2 is born.
Also depending on what you have 1st, (boy or girl) and what kind of child they are, often changes your ideas if you want more. Many people want at least one son and daughter, so when they get 2 of the same right away, they try again (keep in mind my parents had to have 3 boys before they finally got a girl.)