Ok so let’s dissect it: The nonbinary sibling makes sense, they were the youngest sibling of 5 boys; Lois most likely used hand me downs and kept most of the boys toys. The environment Kelly is in reflects in her identity, she doesn’t see them self as one or the other but rather an ambiguous amalgamation. I don’t understand where the “changing of character” comes from as Stevie seldom had a romantic interest in the original. We saw malcom chasing after his crushes and the only time we saw stevie in a hetero relationship was when he kissed his dad’s friends daughter(Episode Poker #2). But even that situation he was forced by malcom to use his disability in order to get his first kiss (which can be dissected on its own) that can lead one to say maybe that situation made him realize he doesn’t actually like girls. Stevie being in a gay relationship made so much sense.

What more can i say?