First off, I'm not trying to start arguments, nor am I telling anyone they can't ship ByaRuki. This is just a rant. If you're a ByaRuki fan, it's best that you move along.
To tell you the truth, when I first heard that people shipped Byakuya and Rukia together, I felt sick. Then I went WTF, because this pairing, out of all the Bleach pairings (besides crack ones) makes the least sense to me. What makes even less sense is the argument that "they're not really siblings, so it's okay!"
Uh. No it's not.
I see this excuse used the most and it honestly makes NO SENSE. Just because two people who were RAISED as brother/sister aren't blood siblings doesn't make it okay for them to start shagging each other. If you're made to think this person is a relative, a sibling, despite blood - then they're your sibling. End of story.
I'll use myself as an example: I'm adopted. I have about 8 brothers. No, I'm not blood related to them, but that doesn't mean I'm going to start dating one of them. Imagine being raised to think someone is your brother and then, suddenly, they want to start dating/having sex with you. To you, this person has been a brother (regardless of blood) up until that point, and all of a sudden they're romantically interested in you? That's creepy. And just strange. I would seriously question the sanity of anyone who honestly thinks that's okay, just because they're not blood related.
So I guess it would be okay for an adopted son to want to date his adoptive mother? Think about that. It's no different. Many people would find that wrong, so why not with adopted siblings?
And another thing, Byakuya promised Hisana that he would take care of Rukia as A SISTER. That alone should be enough proof that he loves her as a brother would, even if you disregard EVERYTHING else in the series. And yet people STILL insist it's "okay." When he said he was going to kill Zommari for pointing his blade at [Byakuya's] pride (Rukia) he was saying that Rukia is literally his PRIDE - the one thing he would protect above all other things. That doesn't denote romantic feelings. He's saying that he would protect Rukia at all costs. Which, by now, all Bleach fans should know protecting loved ones - friends, companions, and in this case, siblings - plays a huge role in Bleach. Him saying he'd protect her doesn't automatically mean he wants to pursue a romantic relationship with her. Ichigo doesn't want a romantic relationship with Chad - and Ichigo protects Chad and the other Nakama. Wanting to protect someone =/= romantic feelings.
ANYWAY that's my thoughts on it. I should find better things to rant about in Bleach besides pairings and yaoi, haha.