Five Months Older
The Second World War had begun, and John wanted to join the army, but he was only 16 years old, and boys were allowed to join only if they were over 18. So when the army doctor examined him, he said that he was 18.
But John's brother had joined the army a few days before, and the same doctor had examined him too. This doctor remembered the older boy's family name, so when he saw John's papers, he was surprised.
How old are you? he said.
Eighteen, sir, said John.
But your brother was eighteen, too, said the doctor. Are you twins?
Oh, no, sir, said John, and his face went red. My brother is five months older than I am.