i feel u. I am in the exact same situation as u. I knew that my mam was cheating since 2 years now. But i did nothing, i always hear her talk to some guy through the phone. And i also heard her say"l love u too" in Amharic to someone.She don't even make much attempt to hide it, she think i am just little kid. But i know everything. I have seen many messages on her phone and it disgusts me to no end. I always just try to ignore it, and it is working i guess. But deep down i alway feel shit. I just dont know what to do. But i won't resort to ur method of killing. I would rather kill myself. But ur hands are tied, u have younger siblings, u have to think about them. If u father found about this and they divorced, ur young siblings will suffer. I don't know what is the right thing to do, but i think u should confront ur mam and just tell her that u know everything. Trust me she wont be able to bear the sheme. So she might stop cheating. But dont hate her for this, i know it is a very bad thing but Everyone has a reason to do something , maybe her husband is not giving her enough attention or something else. But it is ur decision.