I used to believe that twins were always identical.
A childhood belief about reproduction

others believed things like this
- I used to believe that the maps for the United States and Texas were identical.— JTexas
- I used to believe the sound of a flushing toilet was nearly identical to the 90210 theme. — Laurenne
- i always thought twins had the same name as each other— Elle
- i believed if you had sex twice in a row you would have twins— dona
- My friend used to think that having a threesome would mean you would have twins.— Yank
- i used to believe i would 'catch up' to my big brother one day and we'd be twins.— lil' sis