Bros mom died
Aunt (sister of dead mom) adopts bro
Bro thinks aunt (now step mom) loves bro
Bro realises aunt only adopted him to get on the good side of grandpa (her father)
Why? Because he will die soon and aunt wants that inheritance money and other money related stuff
Bro is sick of being used.
Bro rebels against aunt
Aunt keeps trying to control bro
Bro makes a way to threaten aunt because he doesnt want to be controlled or used
Grandpa is very old and has dementia
Aunt doesn't want grandpa to do anything that will put her at risk.
This is what bro is threatening aunt with
(I mightve missed a few things but this is the general idea I got. Feel free to correct or add anything)

I need a tl;dr... about the family issue of ml pls