I mean as a practical matter of time and biology there’s zero problems here? Crack AUs aside, they’re totally close enough in age to be siblings, and we know nothing about Musichetta’s background, so: Musichetta is a Bahorel, full stop, she’s one of the Sister Army, she shares her love for literature and longing for Romantic-style Relationship Drama (with possibly less Actual Death) with her brother, there’s really nothing against it!
…Except that Bahorel and Joly clearly talk about her as someone that Bahorel doesn’t know.
So Not!fic time:
Musichetta, in a fit of wanting to have her own life that isn’t eternally tied up with her loving and large and dearly loved and present and supportive and pervasive and kind of overwhelming family, left home as early as she could with some friends, heading off (as she intended) to Marseille, which she knew might not have as much Adventure as Paris but also knew definitely contained none of her siblings, only to get separated from them (how tragic, how unexpected, good thing she left them that bunch of letters to send off along the way so her folks wouldn’t worry, how very fortuitous) when she fell in with a traveling show (they had a trained bear, okay?? And a camel! And guy who could play seven instruments!), discovered her own flair for performing, ran afoul of a certain small town’s Respectable population, narrowly avoided arrests, took up traveling with a tinker and his sister for a while, got incredibly lost, had Sundry Other Adventures, and finally wound up in Paris!! which was very exciting!!
…and also contained, to her certain knowledge, at least two (2) of her siblings, at least one of which was just CERTAIN to be very intrusively Existing at the world, and so she did the only reasonable thing: had a direct conversation with her brothers where she asked them to respect her privacy and desire for relative independence started going by a new name as a Woman of Mystery and got her friends in Marseille to act as a post-office, sending them letters from Paris with envelopes ready to be sent on again from Marseille, establishing her as having a Very Okay and Not At All Interesting life in a city that was Certainly Not Paris!!, with veeeery minimal specifics being mentioned, ever (they forwarded her mail to her too–along with her allowance, which did complicate the reliability of that a little. BUT PRIORITIES!!).
It doesn’t last very long–less than a year–before the day Joly says, all casual like it’s No Big Deal, “ oh yes, and Bahorel-that’s the friend I mentioned, with the tickets?–is coming round to meet up with us on the way to the theater, oh no suddenly you’re looking very ill” and then there is a very familiar knock at the door, which is then opened right away by someone who clearly considers knocking a token preliminary.
And then there is Such a Scene. Screaming, recriminations, tears, insults and imprecations, mutual accusations, Bahorel and Musichetta both so into the Mood that they only pelt Legle with a FEW cushions when he starts making comments from the peanut gallery congratulating them on their performance. (by the end of the night they’re chattering away together and making fun of the stuffed shirts in the expensive seats at the theater and Joly is having a minor emotional crisis because oh no is there going to be Drama like this All The Time now, and the answer is No, actually the Drama levels go down a bit because while Bahorel definitely has a life of his own and isn’t Always Around the way Musichetta had feared, she does have Family close enough to have dramatic arguments with again and that’s really for the best. Even if they do both tell Joly to Dump the other all the time, but he has brothers and sisters of his own and Ignores it.)
I DID MATH FOR THIS QUESTIONokay so Fantine is probably?? born around early 1795 which means she was conceived in 1794
…oh gad this is gonna be kinda grim
It’s A Fairly Exciting Time for Being French in France
The Bahorels,politically outspoken enough in their own circles to be the object of reprisals, went into hiding for a while during the quickly spinning cycles of Terror-Counterterror-civil war-government crackdown-changing governments of those two years. Not sure they’d actually survive, they left their infant daughter with trusted neighbors, assuming that if they DID survive they’d be back in a matter of months, at most. Maybe just weeks!
Unfortunately by the time they got back, those neighbors themselves had fled, and with rural literacy being what it was, it wasn’t like anyone had left a note– or like anyone fleeing civil unrest really wanted to noise about where they’d gone.
They tried their best to find each other again, but finally got word years later of their erstwhile neighbors…having died, far away.
There was no mention of their little girl–or, for that matter, of the neighbors’ own kids. Kidnapped? Killed? Died of illness? It was all extremely plausible, and no way to know. (“Adopted by friendly strangers” , given the situation, seemed by far the least plausible option.)
It was their last lead, and they didn’t want to give up , but…they were out of options. And kids died all the time, especially in war. It seemed like the most likely outcome. So they grieved and bore it, as so many parents did.
(They try not to worry when the son they had so soon after goes to Paris, out of their sight, because hey, it’s not like he’s an easy kid to lose track of! He can write letters home! That they can read, now! Hell, someday he’ll probably be in the papers.)
Papa Gillenormand Really Got Around. Like, Really Got Around the Space Time Continuum. He’s loved a lot of ladies in a lot of eras, and USUALLY he manages to leave his scattered timelord kids with a comfortable life, but like...look, the French economic situation in the early 19th was COMPLICATED, okay, he got confused about which bank was due to fail, it was messy.
Anyway, this is also how Marius is also Victor Hugo. Timespace troubles are a bear.
In Which Enjolras Gets His Looks From His Mom Exclusively
(basically just the same deal as Javert and Grantaire being siblings-- Dad Javert moves to Paris, gets in good by being a better schemer than Thenardier, and hooks up with a Respectable wife in time, retiring to a nice town in the South of France where no one will ever know him under his new assumed name. He’s just even older when he dies this way.)