THEIR RELATIONSHIP
Just for some variety, here I'm gonna list out the different phases of their relationship.
PHASE ONE: Finn the homophobe, Miles the slut.
This is the biggest. Or at least, the most fleshed out. It spans a while, but can be broken down into a further two sub-categories for ease: spite and friendship.
Finn is a homophobe. Even after marrying Miles, he doesn't get off on the male body, watching gay sex, et cetera. He's not really bisexual, just Milesexual. ;D Miles is a slut. x: He loves the guys, especially the straight ones. The pretty much hated each other at the start, especially considering during their first meeting, Miles punched Finn in the nose and then FInn threw him into a table. Then hit on his favourite faghag. And then Miles kissed him just to piss him off. Oh yes. It was love at first sight~
Considering they frequented the same pub, and Mo (the faghag) and Doyle (Finn's partner in crime) had become instant BFFs, it was sort of impossible to avoid each other. They also end up getting roaring drunk and sleeping with each other a lot, giving Miles a lot of smug morning afters, and Finn a lot of, "GDI I'M STRAIGHT FER ********' CHRIST!" moments. <3
Eventually, the apartment opposite Finn and Doyle opens up, and Mo and Miles moves in. Out of sheer proximity, Finn's miserly leeching of their food and toiletries, and Miles's amazing cooking, they eventually actually sort of become friends. Of course, they often have roaring fights because Finn has a key to their apartment and likes to tease the (countless) blokes Miles brings home, and Miles often wheedles Finn about being Milesexual and not being able to sleep with Mo. But no. They are buddies.
PHASE TWO: Finn mans up, Miles is monogomous.
Miles finally snaps, because actually, it's more than just, "Oh gosh, Finn is actually kind of good looking despite being sorta stocky and big-eared, and it's more than just that broooogue~" and he honestly likes Finn, and Finn makes that hard considering he jumps from demanding Miles nurse him when he's sick and calling on him for favours/food, to calling him a f*****t and generally acting repulsed by him because of his sexuality. Miles goes on a long trip to clear his head and his system of all things Finn, and Finn spends the first week going, "Bah, I don't need him."
Except he maybe misses Miles a little, and struggles with his sexuality a lot, and eventually goes and picks up a few men at bars to figure out if he's gay or if he just likes Miles. A couple of dude-on-dude shags later, Finn finally gets comfortable with having a boner for Miles by knowing that it isn't a general thing, just a secular thing. Oh yes. Finn is Milesexual. So when Miles comes home, with a shiny new boyfriend and a will to move on, and then Finn basically tells him, "Roight, let's date, you're my boyfriend now," there was singing and dancing in the street.
Streets of our mind anyway.
Finn and Miles as an actual couple is adorable, simple because Finn is still shy and flustered about the whole thing, and generally treats Miles exactly the same as before - demanding things, calling him a f*****t, etc. - on the surface, but being exasperatingly cute in secret, like holding his hand under the table when no one can see, buying Miles a gift in secret (and getting loud and angry and violently contests if anyone asks him if it's for Miles), remembering their anniversary (and pretending he doesn't), and even just sneaking into his bed at night for a midnight cuddle (which would be nice if he clipped his damn toenails). In the words of foi, Miles is "purely content and, in a way, really confused. He's really not certain why Finn's returning his affection. He never voices it out loud, but it's there".
PHASE THREE: Finn pops the question, Miles says yes.
As if the two of them dating wasn't cute enough (and it was, trust me, it was), Finn eventually comes to realise that he really is, flat out, head-over-heels, inescapably in love with Miles, which is icky and lovely at the same time for the poor Scottish homophobe, Finn asks Miles to marry him.
Miles says yes.
CELEBRATIONS ARE HAD.
And adorable faggotry reigns supreme.
PHASE FOUR: Finn carks it, Miles is upset.
Finn dies. I mean, he digs up, re-kills, and then dissects the undead for a living. You had to see this coming. Miles did, but it didn't make it any less painful, and for a loooooong time he was just... empty. I mean, you can't even know how much these two luuuuurved each other. They spent their wedding night just trying to mould with each other's skin, no sex at all. Okay, a bj, yes, but no sex. These two really, really, really love each other. And then Finn dies, suddenly and horrible and Miles just...
Gets desperate. And he makes a deal with the devil (who looks like a grayscale Louisianan plantation baron, in case you're wondering) to bring Finn back, in exchange for a number of souls, including his own. So Miles becomes a soul collector for hell, corrupting the innocent and making sure they've got a one-way ticket to eternal damnation, and in exchange he gets to keep Finn for just a little bit longer. Finn comes back thinking it was all just a dream - a really horrible godawful indescribably blood-chilling dream. Miles signs an eternity contract of collecting souls to save Finn from that. He signs himself up for devilfication. And it's terrible and sad and... gets worse.
PHASE FIVE: Finn is in Limbo, Miles is in Hell.
They eventually die, both of them, and since Finn isn't allowed into Hell because of Miles, he's stuck in Limbo. He tells Miles it's because he was just a bit too naughty for Heaven, but by now Finn knows Miles's deal with the Devil, and despite being handed the golden ticket to pass through the pearly gates on his death, he chooses Limbo, because Miles is now officially a demon, and... well... demons can't go into Heaven.
It's all very tragic and strained and Finn has to deal with Miles being a monster while still being... Miles. He freaks out a lot, but in a manly way. And Miles freaks out, in a sassy, vaguely demonic way. And eventually Miles can't take it any more, and makes a decision. There's no going back from his deal, after all, but he can't keep hurting Finn by his very existence. So Miles prepares to cross the line from Hell to Heaven, and completely wipe himself from existence in the process. Demons can't go into Heaven, after all.
Finn catches wind, and hunts him down, catching him before his eternal suicide.
PHASE SIX: Into oblivion.
Miles isn't changing his mind. Finn isn't here to try to. Because there's no going back, and there's no where forward left to go. Just this. And he loves Miles far, far too much to just let him go. And he can't face an eternity without the dumb f**. So, they decide together. Hand in hand. To walk into oblivion.
And even when they're nothing, they still love each other.