Unfortunately, this has already happened. I can't remember the infant's name off the top of my head, but there's at least one semi-famous "trans kid" whose mother decided to trans him from babyhood (iirc he was at most three) because he reached for his sister's pink blanket instead of his own blue blanket. I'm not even exaggerating that, she literally said she knew he was a "girl" because he, a literal toddler, wanted a pink blanket. (But the evil "cis TERFs" are the ones enforcing gender roles, right? ...right?)