Report his fortnite account for stream sniping or inappropriate behavior... Likely he's doing something dumb or being obnoxious knowing his behavior.

Another option could be just changing his accounts password. He resets it, you reset it... Rinse and repeat.

And one more thing to just inconvenience him and be petty... Start hiding trash or rotting food under his bed or in his closet. Also, if he's got chores, make it a point to find a way to reverse them... He's washing dishes? Smear food on the clean ones. Gotta sweep the hallway? Sweep the garage and dump it in the hallway. Be malicious, but enough to wear it's clearly deniable.

It sucks, but what you have is an entitled mother/brother and an enabling step-dad... Most you can do is tell the step dad in passing that you and your sister were trying to get passes for all 3 children, as a surprise. But at this point, now it's best to just save up for a better getaway... An apartment down-payment.

Keep money in your own savings account. Away from the house. Make it to where it is purely a savings, and the card can't be used outside of a bank/atm. If your parents have a problem with that, then tell them it's for college. They can't say no to that.

And if they do... It's time to go with malicious compliance... I can't have money? No need to go to college. I can't have any personal space? Cool then I guess I'll move out as soon as I'm 18.

Either way, when you're older, cut contact... Don't visit, and if you do, make it to where you stay in a hotel or with friends... Trust me... The my house/my rules and my baby boy bs is never going away... He'll be 40 still living at home while mommy spoils him on hand and foot and asking you for help as much as you allow it. Eventually step-dad might see reason and book it. But honestly? Don't get your hopes up.