Ill-Timed Prank

To anybody who can help, I'm seven and I have three younger brothers and my mommy's gonna have another one. I don't know what I'm gonna do if it's another boy. My brothers are out of control. Bobby just chased off a babysitter in the worst way possible, Stephen keeps showing everyone his underwear and Jason, well, he's a Bobby in training. I'm trying really hard to be a good big sister but no matter what I do my brothers are just out of control. Send help if you can. Love, Grace