Sorry we didn't impress you enough, Gatekeeper. But when the OP basically says, "Guys, I'm worried that my YA story is way too graphic,"... I'm expecting some seriously hardcore shit. Hardcore enough to make us all doubt whether it can be a YA or not. I mean, why ask the question?

I read a synopsis with spoilers in it about Tabitha Suzuma's Forbidden, just to see "how out of touch" I apparently am. Apparently Maya and Lochan raise their siblings together and in doing so, grow fond of each other. They have a relationship together. From how the review made it sound, the book tries to rationalize it as two siblings who cultivate a sincere but forbidden love for one another. The reviewer even said that Maya's and Lochan's narrative voices dont feel authentic for teenagers. They are portrayed as competent caregivers and are smarter and more patient than typical 30 year olds. For all intents and purposes, the reviewer calls these characters "responsible adults stuck in teenaged bodies." The reviewer said that the tagline on their copy of the book reads "Sometimes love chooses you." This is a rehashed version of a forbidden love trope.

...this isn't really throwing up any hardcore flags. The "YA genre-breaking" content the OP was so worried about.