A polydin fanfic where Shiro and Lance are in a long-term committed relationship where Shiro is poly and Lance isn’t. They’ve worked it out, though, so that Lance is Shiro’s steady relationship and he can have flings and short-term ones as long as Lance is okay with it. He is because Shiro will go out on dates and screw around with other people, but he always comes home to Lance.
But, one day, Shiro approaches him and tells him that he’s really fallen for one of his short-term flings and would like to see him seriously. Lance thinks this means that Shiro is breaking up with him and is devastated, but Shiro is like “No, not at all! I understand that this is a huge change from how we’ve lived our lives, but I honestly think the three of us can work.” So Lance agrees only if he can meet and approve of this other guy.
This other guy, Keith, is a scrawny, dour tattoo artist who never learned that mid-00′s edge was never in style. Lance hates him at first, both because he’s taken Shiro’s attention away from him and because he just has a nasty attitude. Keith doesn’t win Lance over and Lance is ready to go and tell Shiro that it’s not happening, he cannot date Lane and Keith at the same time, but Keith stops him before he leaves and tells him that he understands. He’d never consider sleeping with another person’s boyfriend before, but he’s also never met a guy like Shiro. And it’s so sincere and Keith looks so genuine that Lance gives him one more date. And then he agrees to a third date. And then he goes to Shiro and says it’s okay.
And it’s fine for a while. Shiro’s date nights with Keith become more frequent. And longer. And Lance is used to Shiro going on dates – he’s been with him for, like, six years or something – but he’s never felt lonely like this. Shiro’s always comes home and more and more frequently, when he’s with Keith, he doesn’t.
Until he runs into Hunk, an old high school friend, one day. They reconnect and it’s almost exactly like old times. He starts inviting Hunk over on Shiro’s date nights and it’s amazing. They play video games, watch bad movies, and talk all night long. Best of all, he doesn’t feel so lonely anymore. Everything’s great.
Then, one night, Hunk kisses him. Lance freaks out. He has a boyfriend. A boyfriend he’s in love with. Hunk apologizes and admits that he had such a huge crush on Lance when they were in high school, but he couldn’t work up the bravery back then, and that’s not an excuse for anything but he figured that, y’know, Lance has a boyfriend but he’s never around that maybe it wasn’t working out for them?
Lance asks Hunk to leave. He’s devastated and feels guilty because he feels like he cheated on his boyfriend and also because he kind of wanted to kiss Hunk some more.
He discusses it with Shiro the next day. He apologizes profusely and explains what’s happens and Shiro goes, “FIRST OF ALL I’m really sorry you felt so lonely I thought I was able to balance your needs with my and Keith’s needs but I guess I got so wrapped up in the newness and excitement of my relationship with Keith that I wasn’t able to give you the attention you needed. I think the three of us need to take the time to sit down and discuss our needs and boundaries. But also WHOMST THE FUCK.”
Lance has never seen Shiro so angry at someone, and he’s worried he’ll make it worse by telling him that, hey, maybe Lance is poly after all and maybe Hunk can be his other boyfriend. He tells him anyway, because there’s no reason to keep lying at this point, and Shiro is shocked and a little confused, but thinks it’s fair for Lance to have someone else in his life. He agrees to share Lance if he has the opportunity to meet Hunk. Lance calls Hunk and Hunk is a little wary at first (’cause he’s certain Shiro is just going to come and punch him in the face) but he agrees.
When Shiro and Hunk are on their date, Keith comes over and keeps Lance company. Lance is freaking out because, oh my God, what if Shiro doesn’t like Hunk? What if he’s still angry about Hunk kissing him? What if he comes back and breaks up with Lance for wanting to see someone else. And Keith is all “Dude…it’s Shiro. Like, he’s got his problems – everyone does – but he also strives to be the most understanding and selfless person they know. And he loves Lance. Like, a lot. Would Shiro really do something like try to ruin Lance’s happiness out of spite?” Lance doesn’t want to admit that Keith is right…but he’s right. His little confidence boost got Lance through the rest of the night and, when Shiro returns, he gives Lance an enthusiastic thumbs-up.
So Hunk joins the family. After a while he meets Keith and they’re both, “ffffffUCK” and start seeing each other as well. They all move in together and live happily ever after.