There are many answers to this and several ways to take the question, but I'll assume you're going for the predictable and feeble "gotcha" route where I say my parents had sex. If not, you can be more specific. My existence still doesn't mean everyone should have children. That's not a real argument. There is no ethical or moral duty to have children and some people are wholly unequipped for the tasks that come after the sex part (leaving the burden to others). My parents irresponsibly had me when they shouldn't have and it resulted in a horrible childhood for me. It happened. I've made the best of it. I love life now. But that doesn't mean they *should* have, only that they could and did by accident. Not every experience is as rose colored as yours, and not everyone is in your position. There are a multitude of reasons any number of people should not have children (or keep having them after discovering horrible genetic conditions, as was the case with a uncle and friend of mine), regardless of your inability to acknowledge or accept that reality.