I dont think it's selfish to not want children, if you don't want children then that's a personal choice and it's one that shouldn't be judged.
I've always wanted to have a couple of kids, I'm very maternal and like caring for people, i think the world has always been a bad place and i do wonder how much worse it will be in 3-4 years when we start a family but i just hope to teach them to see the good in the world and give them a better childhood than my own.