Um…You do realize Holy Rome had a crush on Chibitalia, right? That’s not something he would feel for a sibling. Also, you’re confusing siblings for ruled- over states. Being part of an empire doesn’t make you biologically related. It makes you tied politically. That’s my opinion on it anyway, take from it what you want.
As for Holy Rome being Germany? I don’t think so. I share the theory with many other people that Germany is a new personification that was put into Holy Rome’s body, which explains why he may possess some of Holy Rome’s memories. Basically, it’s like a weird body transplant.
Ellawritesficssometimes 