what are the best ways to calm yourself?

so....your younger sibling did something illegal online and you found out and it really fucked you up. me and my sister are making sure he doesn't go on any devices (we do allow him to watch shows with us or play games under our watch). but our mum...she doesn't even care. she even told our impressionable young 8 YEAR OLD brother THAT ITS OK AND EVERY KID DOES IT. i sorta thought it was my fault since he learnt some things from me but i now realise how negligent my mum is. me and my little brother had a fun time watching tv yesterday, i had to go do some stuff so i waited for my parents to come watch him. SHE LITERALLY GAVE HIM HER PHONE JUST SO SHE COULD WATCH SOME OVERDRAMATIC INDIAN DRAMA. my little brother was always a brat because of her. she always says shit like i could take care of my whole family when i was your age, why don't you teach me how to, then? she didn't even teach me proper hygiene or cooking? i only learnt that from my sisters and my school. today, my brother literally threatened to hit me with a badminton racket just to get his ipad. she didn't even do shit. fun fact: my mum used to work a lot before so i had to take care of his temper tantrums while my sister cooked. i prefer the way it was before because i could at least stop him from doing anything stupid. ugh sorry i ended up ranting about my mum. anyways, i've really changed recently. i've shown my aggression a lot recently. i do admit i used to show my aggression to my younger brother and i don't want to do that again. i shouted a lot today, i don't usually do that and i'm scared of taking it out on him even if he is part of the reason. i just feel like i might crack under all the pressure and might do something bad to myself or my brother.