Cattywampus is a dual POV book starring two twelve year old witches. Catybird looks like and identifies as a girl, but she is intersex and has XY chromosomes. She's afraid that because she's "not a real girl", her magical powers, which pass from mother to daughter in her family, will never work right. Some people might wonder why we need intersex rep in books because it's so rare. I learned recently that intersex people make up 2% of the population, which is the same percentage as the number of natural redheads. No one says natural redheads are so rare they don't need to see themselves in books. An important but non POV character in Cattywampus has two moms, so Ash managed to work in a little bit more queer rep, which is great.
The Sal and Gabi duology by Carlos Hernandez is part of Rick Riordan presents line. These are books written by BIPOC creators and about BIPOC kids featuring the writers' culture, folktales, myths, etc. Sal and Gabi is unusual for the line in that it's more science fiction than fantasy, but it's infused with Hernandez's Cuban American culture. It's not a part of the main storyline, but the MC, Sal Vidon, is aromantic and asexual. He's at an age when many kids are having their first crushes and even starting to date, and Sal makes it clear that crushes and dating are not part of who he is. I love how it's woven naturally into the story and doesn't feel forced.
The third book pictured is the second in the Magnus Chase and the Gods of Asgard series, by superstar "storyteller of the gods" Rick Riordan. One of the important secondary characters is Alex Fierro, who is genderfluid. Alex most often identifies as a girl and uses female pronouns but sometimes identifies as a boy and uses male pronouns. Alex and MC Magnus even have a conversation about what it means to Alex to be genderfluid and how it's different from someone who is nonbinary and uses they/them pronouns. This storyline fits perfectly into the Norse mythology that the series is based on. Alex is the child of Loki who, in the myths, was usually male but was sometimes female. Usually if Loki has a demigod child he is the child's father. In Alex's case he appeared as a woman and tempted Alex's father. There's some good queer rep in Riordan's Heroes of Olympus and Trials of Apollo books as well.
Of course these three books aren't the only queer MG books out there. They're just three that I love enough to own copies of. A few more I've read this year are Kacen Callender's King and the Dragonflies, which features a middle school boy coming to terms with his older brother's death and his own sexuality, The Only Black Girls in Town by Brandy Colbert which stars a girl with two dads, and The List of Things That Will Not Change by Rebecca Stead, which tells the story of the MC's dad getting married to another man. The third book in the Love, Sugar, Magic series by Anna Meriano deserves an honorable mention for its portrayal of two boys who might, or might not, have a crush on each other. At this age a lot of kids are figuring out their feelings of attraction, and I love that this was worked naturally into the story. Finally, another honorable mention is Sarah Kapit's Get a Grip, Vivy Cohen, which features an important subplot with Vivy's brother realizing he's gay and starting to date another boy. There are other books that casually mention a character having two aunts or two uncles who aren't featured in the book or a kid at school who has two moms or two dads. This has become common enough that I don't even have a specific list of books with this in mind.
I don't feel like I'm qualified to write a main character who is genderqueer or attracted to the same gender or multiple genders because that's not my experience, though I may try it with an important secondary child character someday. When I wrote my first MG book sixteen years ago, queer rep wasn't even on my radar. That book will probably never see the light of day, not unless I rewrite the whole thing. I may work some casual queer rep into it, but it wouldn't be the focus of the story. The second manuscript I finished, which, after six months on the shelf and then a massive rewrite, became ANNA OTTO IS NOT A HORSE GIRL features an important secondary character with two moms. They're only on page once and only mentioned a handful of times, but I specifically put them in because I wanted kids with two moms or two dad to feel seen. My WIP has more queer rep, though it's mostly in the adult characters. Two women who will be important mentors to the MC are married to each other. I'm still working out the details, but the book will also have asexual rep, which I can write from my own experience as a woman on the asexual spectrum. Someday I'd like to write an asexual MC, but, since I didn't realize I was on the asexual spectrum until I was in my 40's, it's more difficult for me to imagine writing a young adolescent who is actually aware of their asexual identity.
Whether you, your child, or a child in your life as a student, library patron or other non family role, identify as part of the queer community and these books can serve as a mirror or you simply want to read or have the kids in your life read books featuring a diversity of experiences to better understand the world, there are a growing number of books in the middle grade realm that will do just that.