I don't think it matters... I know only children who've turned out fine, and ones with siblings who were little brats haha. I've heard of some couples only intending to have one, and then changing their minds later after its born, and vice versa.... So you can definitely keep your options open. If you have a baby, you can see how you manage the first year before deciding. I've never had kids, but I imagine the first year would be the most full-on....