No child is born in the wrong body. Anyone referring to "trans kids" etc can safely be assumed as a nonce because intrinsic to the transgender thing (aside from the matter of it being a cult - it is) is the matter of genitalia - that, according to the evil myth, in order to "transition", a person has to surgically alter their genitals.
There is a semi-hidden genre of pop-art obsessed with "trans kids", one of the worst - but by no means the only - proponents being a French Canadian called Guillaume Labelle ("Sophie Labelle"). His material focuses on twee, pastel, woodlandy, androgynous, childish characters who moan all the time about how oppressed they are while at the same time being profoundly preachy and unlikeable, never getting out of people's faces and so on. The characters, such as they are, are two-dimensional and talk in paragraphs straight from a Maoist playbook for the hard-of-learning.
Labelle's kids (among others in the genre) talk explicitly about things like sex, organs, endocrinologists and so on. Reviewing the material of Labelle over a long time, his stuff changed significantly some years ago, becoming much more professional in appearance while his characters became simplified and more commercial - the influence of this important change seems unknown.
It transpires that Billy Labelle is by no means the only proponent of this disgusting material and, indeed, groups exist to share it on Tumblr - see the main picture accompanying plus high definition copies within the thread …