It’s definitely canon that Joly and Bossuet have both been involved with Musichetta, and that Joly and Bossuet live together more often than not, and are in general Partners. From Preliminary Gayeties (4.12.2, Hapgood Edition):
Laigle de Meaux, as the reader knows, lived more with Joly than elsewhere. He had a lodging, as a bird has one on a branch. The two friends lived together, ate together, slept together. They had everything in common, even Musichetta, to some extent. They were, what the subordinate monks who accompany monks are called, bini.
And of course it’s established way back in 3.4.4 that Joly and Musichetta are An Item! Hugo never specifies their relationship beyond that; you can headcanon a full-on poly trio, Musichetta being on-again-off-again with both of them, Musichetta having dated one or the other of them first, both of them having dated her at some point before realizing that actually they’re just gay together, whatever. Current LM Fandom (and I very much include myself in this) has generally settled on the obvious poly reading.
If you were to pin me down and ask me under duress what I think Hugo Really Intended in full cultural context…? Honestly, I’d hazard that he intends them to be an established Relationship Triad. And probably one with minimal drama about it! Like, really-really, that would be my honest cultural-context-based, broader-reading supported interpretation. But I do think Hugo was probably thinking of the three of them according to a specific formulation that would have been recognized as a pretty Standard Trope by his readers.
after an incident in 2012 Joly, Bossuet, and Grantaire try to avoid pirates and mariachi bands at all costs
but then Marius and Combeferre decided to throw Courfeyrac the best birthday party ever, which included a band of pirates and a mariachi group
it does not go well
at least three things are on fire, the cake is stuffed into a trumpet, there’s for some reason a giraffe for which they’re all banned from the Parisian zoo, and Grantaire, Joly, and Bossuet are in a rowboat in the Seine, frantically rowing away from the police and some very angry pirates while Grantaire’s playing an accordion he took from the mariachi band
This is, without question, the best post that anyone has ever tagged me in.
But now I have to wonder, what was the original incident? Did Bossuet accidentally steal a trumpet from one of the mariachi players, forcing them all to take refuge among the pirates (which of course backfired because, as everyone knows, pirates prefer the low brass instruments)? Were they drafted to serve as extras in the mariachi band because the lead singer wasn’t wearing his glasses and mistook their pirate costumes for mariachi outfits, only to mortally offend the band members with Joly’s fantastically awful sense of rhythm? Inquiring minds want to know!
they were running away from Madame Houcheloup, whom they had mortally offended, and they came across a pirate ship. the pirate captain was having a birthday party with a mariachi band as entertainment.
the three of them stole mariachi costumes to escape her wrath, and as always with these three, things went wrong. things went so wrong. it’s hard to believe how wrong things went.
they ended up accidentally sinking the ship, insulting the captain’s honor by yelling that captains have to go down with them ship- that’s the rules of being captain, ruining the mariachi costumes and instruments, and starting a fist fight between a mariachi player and the first mate.
but the worst slight was that Joly offended everyone with his awful sense of rhythm while playing the maracas.
Grantaire who gets a big dopey smile when he’s genuinely happy is my literal weakness.
Like, Jehan says something about how cute dark curly hair is with bright blue eyes and nudges R. And it takes a while for it to register and then there’s just this massive smile on R’s face.
Or Bahorel tackles him to the ground in a fight but they end up laughing because they’re both too ticklish for this shit and once they catch their breath, R’s smiling so broadly it hurts.
Or Joly and Bossuet plan a mini flash mob for R’s birthday and his smile takes a few seconds to get there but days to leave.
And the first time Enjolras said he loves him, he thinks R’s mocking him because he’s kind of smirking but it slowly grows into this gorgeous smile that R promptly buries in Enjolras’ neck.
Ugh.
Grantaire with this rare dopey smile that is literal perfection.
all of the amis expect the triumvirate apartment to be impeccably organized and spotless and function like a well-oiled machine
in reality courfeyrac can’t tell their clothing apart when he folds the laundry, enjolras always vacuums at the worst possible time, and combeferre can never find a clean pan with a matching lid to make them dinner in
so basically they end up smushed onto the couch eating takeout and wearing each other’s clothes nine times out of ten and it’s like their dirty little secret that being emotionally compatible doesn’t necessarily mean they’re roommate compatible
and they’re just fine with that
conversely, the joly/bossuet/musichetta + grantaire household runs so well that bahorel actually thinks he’s stepped into an alternate universe when he visits
¯_( ಠ_ಠ)_/¯ 