When is too old to still have a babysitter?

Im 10 and im a girl and when my moms out im in charge of my big bro Mark whos 15. Ive been doing gymnastics since i was 3 and ive been lifting weights since i was 5 to make strength for the gymnastics and since i started ive been lifting 2 hours a day every day. So you can probably guess im really strong now. My bros soooo skinny his arms are like chopsticks. When i was 6 and he was 11 i beat him in arm wrestling and now im way way waaay stronger than him, like now i can beat him in arm wrestling if he uses 2 hands and i use 1. Hes also really immature and he is always breaking stuff and doing bad things and he makes tantrums a lot. 4 years ago he was running round and knocking stuff over and my mom was yelling at him and i was sick of it so i caught him and picked him up and carried him to the couch, pulled him on my lap and spanked him. That made him stop and my mom was really impressed with me and after that she used me to punish him. When he does something wrong mom calls me to spank him and when im not there she says 'wait til your sister gets home!' lol. When mom goes out im in charge and Mark has to do what i say, i make him eat his veggies and go to bed early and i give him a bath and stuff like that, and if he missbehaves i spank him. Sometimes he tries to fight me but hes sooo weak, like im stronger than a normal boy his age and hes even weaker than a boy my age! So i can over power him really easy if he tries to fight back and its actually pretty fun pinning him.

I don't think that's fair

Nah its plenty fair. You dont know my bro, hes such an idiot. Last week he stuffed a bunch of stuff down the toilet and blocked it up on purpose and yesterday he threw a ball around in the house and broke a window. Before mom put me in charge of him and got me to spank him he was even worse. If he didnt have a babysitter when moms away hed probably burn the house down lol. Im smarter than him and more mature and way stronger so i can control him easily so it makes perfect sense that im his babysitter. Like when moms away its just us 2 in the house and it doesnt make sense to hire another babysitter, i dont need one and i can do the job way better than anyone else. It doesnt matter that hes 5 years older than me.

Im not mean to him i take good care of him, i make sure he eats his veggies and does his homework and goes to bed early. I wash him real good and i let him watch tv for an hour if hes been good. I only spank him when he does something bad or if he disobeys me or talks back to me. Sure its embarassing for him to have to obey his 10yo sister or get spanked but its his own fault, if he wasnt such an idiot he wouldnt need a babysitter or i wouldnt need to spank him.

I agree, Wayne. It's not fair.

sounds fair . and i had baby sitters that were younger than me