As a Child up until the age of 7 I used to believe that when grown ups reached a certain age about 70years old, they started to get younger again until they became children, then babies then would disappear totally.
A childhood belief about getting older

others believed things like this
- I used to think that only grown ups were "people".Children to me were no people ,they were just children.— Minny
- When I was a child, I thought that grown-ups were adult.— Gloria
- that as I grew up, my parents would "grown down," then I would be the Mom and Mom would be my child.Anon
- When I was a child, I believed that grown-ups didn't lie.Anon
- When a grown-up is shown as a child, it was actually them, and the film took 20+ years to produceAnon
- When I was a child I used to believe children were being brought by stork.— Matteo