I grew up in a mixed family with my(f) biological brother and sister, as well as our step brother and sister. Each child was around a year older than the next youngest, so our teenage years were a total nightmare for our parents. We're all in our 20's now.
For most of my adolescence, I thought of my step brother (SB) and sister (SS) as my favorite siblings. I looked up to my SS very much--we shared a room for most of my childhood, made friends with each others friends in HS, and she got me my first job where she worked. She moved out before she because she thought my dad gave us preferential treatment.
After graduating, she moved to a small college town a few hours away (not actually to go to school) we hung out a few times, but not since I moved out of state 3 years ago. She has flaked out the last few times I've been in town, so I've decided to kind of stop trying, it's just not worth my effort.
SB and I just generally had each others backs. We were one grade apart and ended up taking classes together in HS. He and my younger brother (YB) almost always shared a room. They would get into fistfights as kids, not so much as they got older, though. As the last two kids living in our parents house, we were best buds. I moved out during a short vacation he was taking, I just couldn't stand the ridiculousness of our parents anymore. After I went off to college, he got back with an old girlfriend. They're working full time, living in an apartment in the boonies, and I think doing mostly okay. It's been difficult to keep in contact with each other.
My older sister (OS) was my nightmare as a child to both me and our YB. She and SS got into a few fights in middle school, and were generally at each other's throats. Because SS and I were so close, I ended up siding with her. She one time slapped me so hard across the face that I got a black eye after we were forced to share a room, so I SS ended up getting to share the bigger, nicer room with me instead. She and my step mom really did not get along (our stepmom is actually Cruella DeVille on heroin, though, so it's understandable.) She met her current hubby in high school, and moved to live with his before she was 18.
She's actually become a much better sister since then. I used to really hate her, but she became happier and nicer after moving out on her own. I stay with her every time I'm in town, and have a genuinely nice time hanging out. She can be very much like my dad sometimes, and still will snap into super-bitch mode every now and then, but overall we have a much better relationship now than we ever have.
My YB and I have gone through many periods in our lives of being either best friends or worst enemies. He moved out of my dad's before he finished middle school to live with our mom, because our stepmother was too much for him. He had anger issues as a kid, and contributed to more than his fair share of household fights.
He struggled to finish high school for I think 6 years or so, but ultimately got his diploma (:D) before entering the army. He was very excited to go at first, then super scared before training. He made it through, though!. He's now barely 20, and called me the other day freaking out because he doesn't know what he's doing with his life (answered with: nobody does, brah.) I hope that one day we'll be able to live closer to one another.
I don't think my dad favored any one of us as kids, but definitely spent much more time on activities he would share with the boys like shooting, gaming, etc. Our stepmom favored me over my two bio siblings, but like I said before was horrible overall, to me more than her own kids, but even to them as well. My OS has cut all contact with her, my YB and I actually held an intervention of sorts a few years back trying to help my dad out of the shitty relationship, but nothing came of it.
I think my mom is most proud of me, and that we two have more in common than she and my brother or sister. My dad might be the same way, it's hard to tell with him, though.
That was an interesting look into my own psyche.