Summary: there's friends and then there's 'friends' and sometimes bromances trump romances.

Note: Not up to date with Grey's, so this is set around late season 8, just after Owen and Cristina's issues. Written in one sitting, not beta'd, not even edited, because I'm lazy. I'll probably delete this at a later date if I decide it's too unpolished and head-vomity.

Title from Taylor Swift because I'm disgusting and shameful like that.

Derek watches Meredith and Cristina, and sometimes he wonders. Derek's never thought Meredith didn't love him, or wasn't in love with him, but sometimes he wonders if she loves him best. It's a logical enough question to come to, watching her and Yang together.

The thing is, they're best friends, but Derek's had best friends, and he's seen people who are best friends together, and it's not really quite like that for Meredith and Yang. Sure, they have their arguments, and sometimes they won't talk to each other for days, but it's still not right.

Take Mark, for example. He's been Derek's on-again, off-again best friend in what seems like forever, and Derek loves him like he'd probably have loved a brother, but he's not the most important person in Derek's life. Once upon a time, he might have called Addison that. After she cheated on him (and probably a little before that, too), he didn't really have that one most important person anymore, but Derek abandoned Mark for it all the same, because there are some things that aren't forgivable, at least not for a long time.

Most people, probably, in that situation, if their spouse cheats with their best friend, won't side with either, but if the do, odds are, it will be with the spouse, which is weird, if you think about it, because one's best friend is not accountable to one regarding who they sleep with, but one's spouse usually is. But it is the way it is, and though the person most likely to hurt you (because they have the best access to your vulnerabilities) are your most important person, they're also the ones you're most likely to forgive, and so usually it's the spouse who gets forgiven.

It hasn't ever eventuated, between Meredith and Yang, for two reasons. One, because they have very different tastes in men, and two, because they'd probably never let a man come between them, and one would always back off because she wouldn't view the man as worth giving up the other for.

Derek grew up with sisters, okay, so he knows women. He knows how they are in a vacuum, he knows how they are around other people, he knows how they are around other women, specifically. They form alliances, against common enemies, and sometimes they get along when they don't view the other as a threat, but the second there's any sort of comparison or competition between them, be it for the hot guy or the best outfit, the claws come out, and the best they ever manage is a tentative frienemy-ship.

Men are different, in some respects, but though they compete less, or less instinctively, at any rate, they still form alliances based on common enemies, or at least common ground of SOME sort, be it football or beer, or bitching about women.

Yang and Meredith, they do have common ground, of course they do – they're both emotionally stunted surgeons (though the former descriptor is pretty redundant), they both have trust issues and both love drama to the nth degree, but that's where the similarities stop. They're night and day, yin and yang, no pun intended. They make up for each other's failings, fit into the pieces missing from each other. Yang is cold and socially clueless (or at least socially unwilling), Meredith is a natural crowd pleaser, much though she tries to fight it. Yang likes control, precision, perfection – and Meredith does whatever feels natural and comfortable. Yang doesn't know what to do with herself around children, and Meredith is a natural mom. Yang can't express her feelings for shit, and Meredith wears her's on her sleeve.

They fit, is what Derek's trying to say, and it's not that he and Meredith don't, (they do, they're similar and different enough to work) but Cristina got there first, got into Mer's head and heart first, and frankly he only gets to be with Meredith because Cristina allows him to be, because she could have vetoed him at any point, but didn't.

He can sort of see what it was like for Owen, why he couldn't hack it, why he gave up on taming the beast.

Yang's been saying she doesn't want kids till she's blue in the face, and maybe Owen could have dealt with that in time, could have forgiven her, if it wasn't something personal, if it was just thing about her, a quirk, an oddity, like not eating tomatoes or being allergic to shellfish. Maybe if Yang didn't babysit Zola and play with her and spoil her rotten, if she didn't smile stealthily and automatically whenever Mer holds Zola and makes those goo-goo faces at her. Maybe if it hadn't seemed to Owen that Cristina just didn't want babies with him, maybe then he could have forgiven her.

It's not that Derek thinks Meredith would cheat on him or anything, no, it's not like that. But it almost makes it worse, that it's not about sex. He thinks maybe it wouldn't even occur to either of them, frankly, because for all Meredith tries hard to be rebellious and hardcore, she's really so straight laced it almost hurts, and she's probably never so much as kissed another girl, even if Yang to her is so much more than just another girl. Yang, Derek thinks, might have experimented in her youth, but she's settled into what she perceives as her identity now, and it would probably take a hurricane to make her revaluate herself at this late date, and anyway, like he's said, it's not about sex at all, anyway, is it?

They're each other Person, how rightly they diagnosed that, and they're not a Person, they're the Person, and they're who the other gets most of their emotional and social gratification from, they could quite happily live on a deserted island (as long as anaesthetised patients continued to be brought over for them to cut open) and never need anyone else. They're soul mates - the Twisted Sisters - and it's scary how jealous Derek sometimes gets of that, even though he knows that if he brought it up with Meredith she would first stare at him blankly and then laugh.

Derek's married Meredith, and he wants it to be forever, he wants to grow old with her, and though he doesn't completely hate the notion that Cristina will probably always be a part of their shared life in a way no other 'friend' ever is, but somehow, he thinks it's not him who's going to have to make room for Yang, but her who might acquiesce him a tiny corner. Sometimes, in his darker moments, Derek clearly visualises Meredith and Cristina, old, sitting in bed together, Meredith knitting, Cristina bitching about the workplace that's trying to force-retire her as Meredith smiles and placates her. Sometimes, he thinks that sooner or later, he will fade from Meredith's life, and whoever Cristina has going on will fade too, and they'll move into a house together and raise Zola and bitch about work and knit together.

Sometimes, Derek gets the feeling he's only a minor character in the life adaptation of the Epic Love Story of Drs Grey and Yang, and his exit cue is coming.

Usually, though, he blocks it out, and smiles right back at Meredith when she grins and holds up Zola at him, and pretends it's forever.

end