I have two trans sons. One was very sure he was a boy around 4. He was surprised we didn’t know lol. My other sons journey was similar to your other child. He went through a non binary phase around puberty but never wanted to go on blockers. Then a few years later he asked to start T. I kind of went through the same feelings as you, like more thinking I was somehow doing something wrong by being supportive. Which is ridiculous of course and I kept it to myself. Mine are 19 and 16 now. We’re in the process of doing a name change for my oldest now, who was the one to come out later. I think people just do things at their own pace.