I've been trying to find this manwha but I forgot the name of it as well as the storyline....

I've been trying to find this manwha but I forgot the name of it as well as the storyline. I think it's about this (previous ruler?) who lost his memory and is now a servant. The current ruler (or maybe the ruler's son) treats him badly, but has a crush on him. The sister is nice, but she left to go somewhere, so now the previous ruler has to attend to the current ruler. I think they were childhood friends. The mc is blond and the other guy has dark hair. There's another ml, but mc doesn't remember his past with him.

This probably sounds really confusing, but if this sounds familiar to anyone, please post the link! TY!