Same. I was probably the worst of the bunch, but was basically treated like I was the only bad kid. My siblings definitely did some naughty things, but somehow they weren't reprimanded like I was and I was treated differently. My step brother was constantly bringing girls home, going to school events, going to visit friends, leading a very active and social lifestyle. He was allowed to have girls stay over and sleep in his room with him. My step sister played this goody-two-shoes role, which was a complete facade, and thus got away with everything. She'd get to stay over with friends, go out for entire weekends, go on vacations with friends, and once she even confided in me on how to sneak around and make up this story to our parents so that she could spend a weekend in a cabin alone with her boyfriend. My sister had a long time boyfriend, they dated pretty much all throughout high school, and she was allowed to sleep over at his house on weekends.
Me? God forbid should I ever have a boy over. When I lost my virginity, I was grounded. When my step sister lost hers, no one found out about it except me because I borrowed one of her Cosmo magazines and found a used condom hidden between the pages. And we all knew that both my step brother and sister were sexually active.
So since I was treated differently, I had to sneak around more, which of course worked against me since that made me look even worse, when in reality I wasn't doing anything different than my siblings, it just seemed like I was bad.