I was born on my sister's second birthday. For years, when either of us went to a friend's birthday party, we could not understand why THEIR siblings weren't also celebrating a birthday!
We had assumed that all siblings were born on the same day.
A childhood belief about birthdays

others believed things like this
- My friend thought it was SO WIERD that he was born on his birthday when I told him he was.Anon
- I used to believe because I was born I Abe Lincoln's birthday I had a better shot at being President.— END
- I thought I was such a lucky and special kid, because I was born on the exact same day as my birthday.— ricolarno
- Since I was born on the 4th of July, I really thought the entire country celebrated my birthday.— -Stoddard
- Up until I was almost 11, I thought that a birthday suit was a special outfit you wore only on your birthdayAnon
- I used to think that a birthday suit was a special outfit you wear on your birthday— Bri