WIBTA for asking a boy’s family for an item that he borrowed from me before he died?

So I’m 14/M, and almost three weeks ago I let a boy in one of my classes at school borrow my sweater. He said he’d give it back to me after his mom did laundry, but unfortunately a few days after this happened he was killed in a bad car accident. Obviously I knew it wasn’t okay to say anything before his funeral, but now that it’s been a couple of weeks I’m wondering if it would be okay to go to his family and ask them for my sweater?

The main reason that I’m not sure if it’s okay to ask is because I’ve never met his family at all and I don’t think they even know who I am, I knew this boy from being in school together but we weren’t friends or anything.

I did ask my older sister for advice but she said that if it were her, she just wouldn’t ask because she would be worried about upsetting the boy’s family. And I do agree that if it was just any random piece of clothing I wouldn’t bother asking at all, but this is a sweater that I got on an important trip and it has the name of the place where I stayed so I do care about getting it back. I only let him borrow it because it was an emergency.

So WIBTA?