Mostly human is sexual aromantic, with a preference for sex with a friend or potential friend rather than, say, hookup culture.
"So friends with benefits?"Succubus is largely the same way but she actually does have a smidge of romantic, which is rare for sex demons. (They're almost exclusively completely completely aromantic.) Very importantly: she's from a Succubus/Incubus community that believes strongly in consent which is far from universal in the species.
"I never liked that phrase. All friendships have benefits, otherwise they wouldn't be friendships."
Runaway kid is initially young enough that sexuality isn't really known, but ze is sure about being binary conforming gender fluid. (Whether he's a boy or she's a girl changes, but ze is always either a gender conforming boy or a gender conforming girl.) Had to run away from home because dad didn't want "his son" to be a "sissy" and mom was pissed off because "being a woman isn't a part time job."
Mostly human finds runaway kid and knows exactly where ze can be accepted.
Succubus/Incubus culture is very welcoming into non-cis people. The species never has a "body doesn't match identity" problem (they're not human and thus they operate in different ways) but ... while every Succubus is female, every Incubus is male, but the demons can freely change between the two.
They've got full time Succubi who were born Incubi, full time Incubi who were born Succubi, and a large contingent who change between the two all the time. While they fundamentally don't get genderqueer people --or a lot of human gender sexual identity things-- they make an effort to be accepting on those fronts and generally do a good job of it.
Runaway kid's gender identity is practically a prominent Succubus/Incubus identity anyway and even if it weren't the culture would be accepting of zir identity, since Sucubus' group is all about consent, the comon dangers associated with Succubi and Incubi don't apply.
Skip to years later.
Succubus has adopted runaway kid and loves zir a lot but has a bit of a crisis when she realizes that runaway kid is asexual aromantic. Mostly the asexual part. So many of the things that she had panned to share with her child go up in smoke with that revelation.
Both of them end up talking with mostly human.
And that covers all that I've been trying to write in these fragments.
Scene one: Succubus and mostly-human meet for the first time.
Scene two: Mostly human meets runaway and brings zir to succubus.
Scene three: Sucubus talks to mostly human about discovering her child is asexual and her feelings surrounding it. After she leaves, runaway talks to mostly human about the Succubus' reaction. Mostly human's general reaction to both is: You love each other as child and parent, pretty sure that's more important to either of you than the sex thing.
I'm not having any luck actually writing it.