I'm 26 and absolutely do not want to birth children. I was very surprised to read that people are called selfish for not wanting children, I really believe it's the other way around. For us, with my husband and I's effed up genes with a high probability of passing on depression, cancer, diabetes, etc, it would be thoroughly selfish of us to have children. We both can't relate to this narrative of leaving a legacy behind, it feels like an exercise in narcissism, creating a child in your image to look after you in your old age. It's completely beyond me

They'd be a person in their own right who would owe absolutely nothing to us. Our hypothetical biological children with my husband's bright eyes and my wild curls would be lovely, kind, polite humans in our imaginations, which is where they'll stay.
Aside from wrecking my body with childbirth and extensive post-birth complications, childbirth doesn't feel right either because of how overpopulated this world already is. There are already too many children in an abysmal foster care system who already need love and safety. We hope to foster and adopt children in the future when we're ready (along with more cats and dogs). We're just saving up to get there. They'll be ours in every sense of the word, it just doesn't make sense to birth more children.
Thank you for all the differing opinions on this thread, I feel very passionately about this and I've really enjoyed reading everyone's experiences/thoughts.