I think saying it's selfish (regardless of what definition your using...) is a bit silly tbf. My family is plagued with degenerative illnesses, both physical and mental, stretching back as far as any living relative can remember. Is it selfish of me to not want to pass those on to someone else? I'll be the first to admit that this certainly isn't the only reason as to why I will never have kids, but it's certainly a large contributing factor.