MC was a cousin of the usurped king/nephew. Nephew/king was a child & couldn't really hold office = no real power. The state was being runned for him until he becomes of age. The current uncle/king killed the nephew/king's supporter - i.a. Mc's father, olders brothers or anybody who supports nephew/king. Yes - they were scapegoats. The last chapter explains an plot to kill/uncle but that could possible be an excuse to get rid of nephew/king supports therefore solidifying his 'rights' to the thrown. MC is considered a traitor of the uncle/king. He can never hold office, or be a man of nobility despite being noble. Any support to MC will lead to suspicion of supporting nephew/king & lead to his demise, i/a. jail or death.
I hope this helps
tldr: MC, a noble cousin of the usurped child king, is branded a traitor by the usurping uncle who eliminated the king’s supporters to secure his throne, making any allegiance to MC a dangerous act punishable by imprisonment or death.

Can someone explain to me who our MC was again before his family was killed? I think it’s been too long and I’m forgetting the actual plot haha.
Were they killed for no reason? As a scapegoat or did they actually do something wrong?