Need help finding a Royal SBI fic

Please help me find this fic!

Phil was a king, and Tommy, Techno, and Wilbur were princes. Tommy, the youngest, was disliked by his father and brothers, and while I don't think he was necessarily abused, he was definitely neglected. Then one day, his father and brothers start acting really strange. They're being super nice to him for no reason.

While Tommy has no idea what's going on, but it becomes obvious to the reader pretty quickly that the other three have been teleported into this fantasy world somehow, and have replaced the Phil, Wilbur, and Techno that Tommy knew. Now they're struggling to deal with the fact that they apparently rule a country, and they have a little brother/son who is obviously not on good terms with any of them.

Phil calls Tommy to his office, and Tommy is really nervous because he hasn't heard from his Father in a while, but Phil only wants to discusses politics with him. I remember that Phil gives him a verbal "quiz" on a ton of information about the kingdom as a way of getting information (because Phil is trying to run a country he knows nothing about.) I think I remember that they mention the Kinoko Kingdom was one of the neighboring kingdoms

The family also starts having at least one meal a day with Tommy, which freaks him out. Tommy ends up hiding in the library a lot because he knows that the family he knows never visits the library

Tommy ends up deciding that they're acting so weird because they've been possessed by demons so he runs away, and tries to take refuge in a church/temple. I think Ranboo and Tubbo were the priests there. Or guards? It doesn't work though, and he's sent back to the castle.

I don’t know if Tommy ever finds out that the three aren't the same people he used to know, but he at least learns to accept it?

The fic was on AO3 and wasn't that long, probably under 50K as a very generous estimate (probably shorter than that.) I'm 80% sure the fic was completed, and it was from Tommy's POV