Romances, huh? Well, alright.
For a successful one, I think I'll go with Deliciae and Madrid. Madrid was heir-apparent to an Amber down to its last handful of Elders. Caine was king in that world, and she was his adopted daughter. Deliciae was Dworkin's much-younger brother, born after Dworkin had run off from Chaos... it was enough of a connection to wrangle Deliciae a visit to Amber, but the Amberites of that world didn't *like* Chaosites very much. Especially Caine.
Deliciae started courting Madrid, I think, for amusement's sake; I don't think he expected it to mean anything, especially to him. He realized it did when Caine called him in and suggested he stop. Deliciae politely declined, and on his way out, passed Benedict going in...
Deliciae's not an idiot. He seriously considered popping back in and telling Caine he had reconsidered. He's still not quite sure why he didn't. Fortunately, Benedict declined to kill the upstart Chaosite, and while Caine has never liked it, Deliciae has made himself into a very difficult man to assassinate.
His relationship with Madrid at this point is very odd. Both of them would probably be, by Earth standards, sociopathic at best. Not necessarily psychotic or murderous, but...they don't connect to people the way normal people do. Madrid was experimented on by (or is entirely an experiment of) Dworkin, and has a Pattern-based battle computer built into the back of her mind...when she's directly endangered, she becomes *very* dangerous. In the meantime, her mind is still half Pattern machine. Deliciae is just the kind of Chaosite who meddles and spins off plots more as a hobby than for any great purpose.
Meera and I were talking the other night about the implications if a couple of our Ambers came into conflict, and it occurred to us that Deliciae would probably be behind most of the defense of the universe he lives in, despite being several steps removed from any formal power base. Only one (out of about a dozen) of the major rulers even speaks to him directly, but he has threads going everywhere. He also occasionally thinks about killing Madrid, just because it would be so easy (he knows all her weaknesses, afterall), and because a part of him is curious if he could do it without subsequently being killed by Dworkin.
They still love each other very deeply, though, at least inasmuch as love really applies to either of their mindsets.
On the unsuccessful note, I think I'll go with Unakai and Patricia.
They're both my characters, and Patricia was specifically designed to be Unakai's partner. (Unakai Walked the Pattern and wished very hard to find Mr, Ms, Or Whatever Right. The Pattern LIKES Unakai, so it tried very hard, punching through several universes.) With controls like that, both in game and metagame, they really should have worked.
Unfortunately, as I'm sure anyone who's ever gamed knows, characters change. Unakai and Patricia were quite happy with each other at first, and had two beautiful (albeit not entirely human) daughters, Jocelyn and Oraela.
Patricia, though, was relatively young, and very much out of her element. She had a bit of a nervous breakdown, and fixated on Rhondia, the Captain of the Guard, and incidentally the person in the castle about as different from Unakai as it was possible to get.
Unakai simply isn't the type to hold anyone against their will.
Their separation was a sharp break; painful, but fast, and she let Patricia go hoping for her happiness. Unakai has recovered from it, honestly, better than Patricia has. Things didn't work out with Rhondia, either, for myriad reasons...it probably didn't surprise anyone around them who was thinking more clearly.