Things between him and the Empress get better so he gets access to his brothers! Turns out the Empress has been fed LIES by her father and his faction about MC BECAUSE she is a caring persons. She's NOT thrilled that her father essentially thought "it best" to trick her into hating her stepson irrationally! The previous incident with her eldest and this one with her youngest made her assume he was a vicious child that wanted to harm her children for attention and as said with this one, he's pushing the "narritive" that this was just a "clumsy assassination attempt cause he's a child to make him look like a vicious "incompetent" danger and further isolate him. Remember his brother thinks because of the lying from his nanny and guards that MC was "a bad kid" and was trying to harm him that day and the knight who was punished was "trying to protect him" and was punished because their father "can't see that the boy is a bad seed" hence his hostility
Now that she and his brothers are on his side (I can only imagine the Empress annoyance, she likely thought WELL of that Knight who was demoted "protecting her son" but now knowing her father lied about MC and the truth was that Knight had acted brashly BECAUSE he knew MC was "unwanted" and assumed he'd get away with laying hands on a royal! I'm sure he went from "alright and hopefully his career will recover" to "May he rot where he's positioned the LIAR") This greatly reduces her father's faction's own actions towards MC since now they can't act "pretending they represent her" it won't curb her father's OBSESSION with controlling MC movements and actions! The man is still STUBBORN in that he sees MC as a potential threat and cannot rest easy unless he knows WHAT (Same with the YOUNGER Duke, it's why they pushed so hard to seperate him from his entourage, such as removing his nanny/aunt! Though largely it was her SIL wanting to send her far away so that her own son's succession isn't threatened by her daughter, bonus by putting into the girl's head that her cousin is to blame for why her mother isn't around and not knowing the full story, believes he's a bad kid, honestly next time she's shown, I won't be shocked that she feels horrid once she knows the full story of him......or things between her and his aunt didn't go well and she still blames him despite not being there, only meeting and getting to know him does she realize he did nothing wrong and she only wanted to BELIEVE in the bad rumors because otherwise SHE would be the bad kid, makes no sense but so does his Step-grandfather and distant cousin/Younger duke's obsession with him LOL! But removing her was the hopes of losing a supporting pillar mother like figure, hoping it might destabilize his mood! Remember MC is doomed no matter what he does, He acts mature, he's viewed as Shady, he acts like a child, he's treated like a Vicious threat, no matter what those who already painted him as a threat will look for ANY flaw to demonize him and justify their own bad behavior, largely cause their BULLYING a child, obviously they don't want to look like the POS to anyone that has a "Hey wait a minute" when they realize it)
As a reminder the Two Duke's actions towards MC are do to self interest! The OLDER Duke wants his line to flourish, and fears ANY success no matter how tiny MC makes risks someone trying to start a succession Crisis, it's the only major reason he worked WITH the Young Duke in trying to take control over the land that should be rewarded to MC because he accomplished the "Alchemist" requirement! If he is given it, it means he has MERIT, and damages the image both Duke's have cultivated of him being a Parasite the Current Emperor refuses to set aside (Remember thanks to becoming Emperor, and to cover up his "roots" his marriage to his deceased first wife was considered illegitiable, by how that went, it makes the Empress his FIRST WIFE, so with that MC is treated as an illegitimate from a FLING! You can guess the Emperor is NOT happy his first love is being treated LAWFULLY as a MISTRESS just to make MC illegitmate to the throne! It is) for "teh greater good of the Kingdom (a JOKE really, the "Greater Good" is those two assholes ambitions no longer being RISKED despite MC wanting nothing to du with Succession! But ambitious people are the worse because in their minds, till you are DEAD AND FORGOTTEN they can
The YOUNGER DUKE is obviously an Antagonist! MC knows his "Step-Grandfather" is only worried about HIS bloodline flourshing within the Imperial bloodline! His actions are only to assure MC never becomes a threat to his bloodline, even if he knows he's OKAYING BULLYING A CHILD. The Younger Duke it's PAINFULLY obvious that he had a HAND somehow in how MC "uncles and grandfather" all "died suddenly" as without his father's secret existance, he was all set to become Emperor! Unlike the Older Duke who if MC is not a potential threat "somehow", he won't harass or bother him! The Younger Duke may still hold Ambition for the Throne still! HE is largely the reason MC "was willing to take all the abuse and hide things from his father" because his father's faction is still small and new compared to the YOUNG Duke, so he could start a coup if he saw the advantage and MC doesn't want to be the cause of it. And of course if he DOES go the route of killing off his little brother's and father, he ISN'T sparing MC either, since reminder is that DAD was Illegitimate and that still gave him a stronger claim to the throne then the YOUNGER Duke! That means MC would IMMEDIATLY becoming Legitimized and made Emperor if anything happened to his brothers (the biggest reason the OLDER Duke is on his ass as well) and the Younger Duke won't tolerate having his path to the throne thwarted TWICE by a "illegitimate" (It's why at the party, MC KNEW things would get INTENSE afterwards cause the reports the Younger Duke was getting painted him as a Stupid Child! Now knowing he is doing Alchemy, even if it's for extra funding and getting the things being DENIED just to harass him, the man got petty, wanting BADLY to get one of HIS spies attached to MC in case to also sabotage him. Imagine something minor you do SABOTAGED simply because it's you doing it, even when it has NOTHING to do with successions, or fame or ANYTHING, just your Peanut Butter and Jelly sandwich, SABOTAGED simply out of petty spite....and reminder you're a child and the petty asshole is a FULL GROWN MAN!