There’s only so much room in a single ask to put things, and it’s ok to not be able to put the context in one ask! *offers you a hug*
Given the context of fiction and that bit of world building, I’m still not entirely certain if the line from the previous ask would be a shitty thing for a character to say or not. I’ve a few world building questions, though, for you to answer for yourself.
First, I’d like to say, the idea of a world where gender doesn’t restrict choices is a fantastic idea, and I love to see how people handle that. It’s not something that I see as much as I’d like, and I seriously hope that’s because I have limited energy to search for new books.
If the society is not divided by gender, what would be the purpose of assigning a gender to children too young to express their own preferences of pronouns and gender? Is it a vestige of a past where gender was binary and restricted choices? One that is still clung to by enough of society that the mainstream cannot entirely excise it?
Does it effect how they’re socialized, consciously or unconsciously, on the part of their parents? Does it effect their choices of expression – in how they adorn their bodies, the clothes they wear, how they cut and style their hair?
Does language still reflect a gender-binary past, or is it gender-neutral in common usage?
Is gender still generally considered binary, even if social structures are in place that mean that genders are effectively equal?
Also, how does society in your world handle those who don’t identify with their birth-assigned gender, including those who aren’t comfortable with either male or female? How does it handle infants whose genitalia doesn’t clearly match a binary? Are they assigned a third gender at birth instead of male or female?
Because how the society you’re building thinks about, talks about, and uses gender is important to why you’re introducing the twins as male and female, beyond the presentation of their external genitalia.
And if the answer to why you’re introducing them as two nominally binary genders as they’re generally assigned at birth in life is because it is a spot of familiarity for readers, that’s an answer you need to know and keep in mind.
Ultimately, I think that if you’re confident in how your society is handling gender, and you know why these twins are being introduced as male and female, than making it clear, even in an offhanded way, that gender is not necessarily fixed, isn’t a bad thing. Just that there’s far more to it than a simple “is it shitty to introduce such a concept in a potentially off-beat manner?”, and that complexity introduces a lot of uncertainty from an outside perspective. Which, in my case, means I tend to want to ask a lot of questions, even if I’m not necessarily asking them with the intent of being given answers.
Ask box is always open if you have more questions on the topic, or just want to bounce other thoughts off me, and that goes for anyone! I enjoy poking at world-building, even when it’s not for my own writing. 🙂