My goldfish (around 13 years old) is curled up on the bottom of the bowl. Is he dying or could he be saved?

We had a previous goldfish which died the exact same way. She didn’t get through the night and was laying motionless on the bottom, even tapping on the glass (lightly) didn’t spawn a reaction. She also didn’t have a breath, not even a slow one. We have already buried her.

The goldfish where this question is about however, survived two nights in this situation. I thought maybe there’s a cure if he’s still alive, like a tablet or an injection. My parents disagree and think we should leave him, say our goodbyes and well, let him die.

What do you think? Please..