They're both fucking her, and each of them knows the other is fucking her and doesn't like it, but they both like their balls attached too much to try to tell Faith who she can and cannot sleep with. It is not that they do not feel jealousy or possessiveness—these two sons of Angel, each sired in a different way, one turned by Drusilla's sharp fangs and one birthed from Darla's cold womb, are each too virile, too much the alpha male, not too, but they bottle up such feelings and repress them out of an even more overpowering sense of self-preservation. Nor do they blame each other; when a goddess like Faith offers herself to you, you accept. To do otherwise would be unthinkable, the profanation of a sacred welcome.
Which is not to say they get together, exactly, Spike and Connor; each reminds the other too much of Angel for that.
Connor calls out an invocation to this Slayer goddess as she is naked underneath him, as he pounds into her furiously, and for the moment, the too brief magical moment, she allows him to imagine that she is his and not the other way around.
Spike is a floor above, but with his vampiric hearing he cannot fail to hear the two beneath him. He does not like what he hears, but Faith is a force of nature which must be respected. Still, for some reason he cannot name, he descends the steps of the Hyperion, not to tear them apart but simply to watch. There they are in the lobby, naked flesh pounding into naked flesh.
He knows they have to know he is there, but they do not pause for several seconds, fucking away until Faith says in between groans, "Well, are you going to get over here or not?" And because a command from Faith is not to be disobeyed, he walks over to them.
"There's—ah!—lube behind the—ah!—desk," Faith says, and Spike obediently fetches it. Seconds later, he has entered Connor from behind. He stretches over Connor's shoulder to place a kiss on Faith's neck even as Connor rises and falls underneath him. With her Slayer strength, Faith can support the two of them on top of her without difficulty. Connor comes quickly, his stamina diminished by now having to fight the war on two fronts.
Spike isn't far himself when he pulls out of Connor as Faith, smiling wickedly, pushes the two men off her. Spike drops to his knees to go down on her, and Connor's head hovers next to his, his body pressed up against Spike, ready to take over at a moment's notice. Spike doesn't need to come up for air, of course, but stops and lets Connor have a chance anyway, then takes back over when Connor does need to breathe. They make her climax two, three, four times before Spike, who has been achingly hard through all of this, finally enters Faith and comes inside her almost immediately.
. . .
They still fuck her separately, but threesomes become more common from that point on. Spike and Connor fall into an uneasy truce; they still don't like each other, but they're more than willing to fuck each other. Sometimes they even do it just the two of them, while Faith's on patrol, desperate even for just the scent of Faith which clings to each other's bodies.
Wesley—who may be fucking her too, they're not sure, but if so is much more discreet about it than either of them bother to be—says it is appropriate, that all of the great goddesses of old had two high priests, one of the light and one of the darkness. At this point, they're not even sure who is which.
. . .
Birth control and condoms are an unavailable luxury in post-apocalyptic L.A., and Faith's far too horny to keep her legs crossed just because she's ovulating, so they really shouldn't be as surprised as they are when the Slayer begins missing her periods.
There's no doubt as to the father; Spike's not even in the running as a vampire, and Wesley, even if he has been sleeping with her, actually has the enviable ability of being able to refuse her when he considers it necessary (and no one doubts for a moment that he's kept track of her calendar). Faith rotates her way through every curse word she knows for three days straight, then threatens to castrate Connor, then fucks him again instead since, hell, she's already caught, so she might as well wait until after she pops out the kid to do the castrating.
The entire team has to put up with eight months of alcohol-free Faith, and are amazed when the Hyperion is still standing when she goes into labor.
It turns out that satisfying horny pregnant Faith is even more difficult than satisfying horny regular Faith, something that Connor and Spike and possibly Wesley were having difficulty managing between them even then, especially as its not long before they won't fuck her nearly as rough as she wants. And then it's not long after that before she has to settle for oral sex followed by watching them fuck each other, and you can be sure that if at least one of them isn't bleeding by the end of it she's going to call foul.
. . .
She wants to name it Angelika, but both Connor and Spike are steadfast in opposing this and manage to talk her out of it. They consider the names of others they've lost, Joyce or Cordelia or Anya or Fred or Buffy or Dawn, but ultimately they agree that none of those names would be fair to the kid. Faith knows what it is like to live in Buffy's shadow; she's not going to saddle her daughter with the same burden.
They finally pick Rose as a reminder of the world they left behind; no one's seen a flower since the apocalypse started.
. . .
Once Rose comes into the world--such as it is--Faith turns her leather jacket into swaddling clothes by wrapping Rose in it, declares her the most beautiful thing in the world (not hard under the circumstances), drinks six beers in one sitting, and initiates an orgy at the baby's cribside. Simultaneously.
. . .
They still fuck her separately, but every once in a while, when the three of them are together, the goddess lets them make love to her.