The question stalled him. He had honestly no idea. There were kids younger than him, kids his age, young adults and old adults. Teachers-- which is what Lupin would always be first and foremost in Harry's mind-- had no real age.

But he recovered from the minor slip and shook his head.

"He didn't know me. But he wasn't my age. Sometime between..."

It was only then and there that Harry realized what that meant for Sirius.