I have never felt a desire to have children. It's often said that this feeling changes when you're older. I don't understand how this would work

I'm 21f and I have never felt a desire to have children. I accept that this is something you either feel or you don't.<br>I see a lot of stories of people who never wanted to have kids but then often when they meet a person they want to share the experience of having a kid with that changes and they want to have kids. <br>What makes that happen? Are people who didn't want to have kids just lying when they said they didn't want to have kids?