It was a decision I made when I first left home, along with eat wholefoods, wear natural fibres, avoid plastics, don't drive just because you can. Even then it was clear to me that the planet didn't need any more human beings, and so I did my part.
I also didn't have the greatest parenting, and was determined not to pass any of that on. The longer I was away and able to be myself, the less this was a worry, and it faded within a few years.
By my mid to late twenties i was helping raise other people's children, and it was clear to me and others that I loved it, it came very naturally to me. So I rethought, and bolstered my original decision with 3 criteria. If I met any 2 of the 3, I might consider children after all. I didn't ever meet 2 of the criteria at the same time. So, resolve not tested, and no children of my own.
I've done a fair amount of parenting though, and you can hand me anything from a newborn to a teenager and I do just fine. It's like activating a different part of myself, if there's a need, I step into parent mode. I've had a chance to know the part of me that is a mother, and I feel very lucky in that.
I've also never had that possessive urge, the need to have children which are my own. I've never understood that, tbh, especially the preciousness of some parents, when they're not remotely interested in anyone else's children. How else to love any child, other than as your own? It's a universal thing, to me. I once said to a friend that I though the real 'earth mother/father' archetypes were people like me, who could shapeshift and parent any child.
I could feel a bit melancholy if I try. It might have been nice to spend more time being a Mum than I've been able to, and to now be surrounded by future generations. However I feel blessed by what I have had.
I still feel clear and happy with the decision I made. Ultimately I cleave to the planet first. Choosing not to have children is my expression of love and care for our beleaguered Earth. It's one of the things I'm most proud of.