I don’t think so. His mother had a hard influence over him and the country so I’m sure that it was her that wanted the artifact. She killed the father and made him king after all, which gave him access to the knights and the mages that killed the MC in his first life. But I see where you could get that from. He doesn’t give off the vibe that he wants to hurt his brothers I feel like he’s trapped by his mom and is forced to do her bidding which causes him to lash out.
She could have been dead already when Planche became king. For eg., she was killed/ assassinated by the king because MC's death.
They said the king was poisoned and she also poisoned everyone one else that she wanted to kill. She also talked about how she had everything she wanted except one thing then they showed a picture of the king that’s why I think she killed him the first time but her plans weren’t able to fall in place the second
But maybe planche killed his mother after she killed his father, I doubt that though since planche honestly didn’t have power and it’s just his mother controlling him
What if the reason Planche want that magic artifact is Callian. Like in 1st life, 3rd prince died and definitely the king might have gone crazy and did some shit. Not to mention the Queen who is already crazy about throne. And Planche wanted to change everything.