uncle/money problem?

okay, so i was with my mom buying a new desk & we only took a car, but the desk was big so we needed a truck.
My uncle and dad were home, so my mom asked my uncle to bring the truck and help us. While he was carrying the desk to the truck, his sunglasses got scratched, i wouldn't say it was badly scratched but you can still use/see through it. Well my mom went home with her car and i rode with him in the truck and he was complaining about how i should pay him or buy him a new sunglasses and i dont think he was kidding, do you think i should pay for it and do you know where to find glass that gets scratched and you can use a cleaner to remove it ?