i'm the oldest. i have a sister that's 3 years younger than me (so she's 13), and we get along really well. we have a lot of things in common, we like the same games, music, all that. our personalities are pretty different, she's the one that talks a lot and isn't shy while i'm the opposite. it works well.
i have a step brother that's like 10-12 years old, i'm not sure. my dad married his mom. i don't know him at all, honestly i often forget he exists. we interacted for a little less than a week over two years ago, so i don't remember him well.