Guys I just made myself cry.
An AU where Prussia didn't die when it was dissolved, but DID die randomly later on, maybe with the last truly Prussian person. He just wakes up one morning and knows.
He goes about the day as normal, eating breakfast that his brother made, chilling, texting France and Spain. But when evening comes, he knows that his time is almost up and he goes to his brother, proud of who he's become. He takes it all in one last time and says "Looks like you don't need me anymore."
And Germany is so confused and slightly concerned because Prussia never gets emotional like this. Gilbert just hugs his brother one last time and then fades from existence, Gilibird going along with him, nestled in his hair.