WIBTA if I stopped babysitting for my cousin when my aunt has no childcare

Throwaway account!
I am 16 years old, my little cousin is 11. I live with my dad and my cousin lives with my aunt and his stepdad.

My aunt and the stepdad go out each weekend into the city and my cousin usually stays with me. At first he was fine and we played together for a bit then he’d do his own thing. But lately hes been doing more and more things to annoy on purpose. I’ve gotten a little list from my notes for examples.

1. my dog is trained, she minds her business and it’s okay to pat her and stuff. she’s mostly a chill dog. she did come from a home of people who hit her, so she hates it when you pat her back. you gotta pat under her mouth, her head or literally anywhere else. I’ve told my little cousin this constantly so he doesn’t get bit or anything. but he’ll wait for my dad to leave the room and he’ll pat the dog on the back then let her chase him around the house. im always able to grab her before she seriously hurts him because she listens to my voice but it’s gotten to a point where I’m considering atleast letting her pounce on him to scare him a bit. he laughs and thinks it’s hilarious to upset the dog.
2. I added a password to my phone after this, but when it didn’t have one he’d open it and message random people on instagram either random or mean things. like he’ll message my friends and call them ugly or fat and stuff. also a lot of my friends little siblings are friends eith my cousins so it’s like ???
3. hides my dads important things. my dad got into a car accident a little over a year ago and so he has a set amount of days to work at home and the other days in work, but my cousin will go in his office and take random papers and put them under pillows in the lounge room, or take safe keys (which hes not even meant to know where they are so my dad constantly has to change where he hides them) or literally just things like his pen and stapler and shit.

anytime i try to talk to my cousin about doing things to annoy me or my dad as a “joke” or to see our reaction and how it’s not okay he thinks it’s even more hilarious. I’ve talked to my aunt once, which is the most recent time I’ve babysat him and she laughed and thought I was laughing about it and was like “gee, boys”. my dad said hes okay to be the one to tell my aunt and he’ll stand on whatever I say but I’m just wondering if this would be a bit of a stretch to leave him without parent care on these weekends. they don’t have friends here or other family that is able/willing to take him btw. WIBTA?

edit: my other account got deleted, sorry about any confusion

2nd edit: no im not the same girl that had a grandma that tested her reactive dog. im pretty sure that post is some ai repost of mine.