Not sure as to whether this story really is about the 'youngest' child feeling that they have been born in the wrong gender body. Several years back, when I was running big numbers of gymnastic competitions for recreational gymnasts, a parent contacted me about their child. Now, aged 7 years of age, they had been born with male genetalia, but had, from as young as two years old, identified as a girl.
The parents had just gone along with the wishes of their child and she had lived as a girl for nearly five years by then. Gone to school, etc. Problem was the birth certificate showed Male. No problem for me, I just told the competition organiser to change this entry from the boys to the girls - was not interested in childs name or club.
I do accept that there may have been more problems as this child started puberty.
One of my g.children at 13 years old said she thought she was gay. Well, that was fine by us, if that is how they felt. Within a year they had changed that to being transgender and wished to live as a boy. Again, this was their choice and we all went along with it. Now, nearly 18 years of age they say they are non-gender. I do sometimes have a little struggle with using what had previously been considered a plural pronoun (they/them), but apart from that no problems.
Their little brother, 11 years old, is very much a young boy - quite definitely, but does enjoy sometimes wearing a skirt as they like the feeling of it blowing out when they spin round. Why should he not wear this if he wishes?
First time he came round to me wearing this, he saw my look and said to me 'clothes should be non-gender based, Grandma - after all, YOU wear trousers, so why should I not wear a skirt?'. I was abashed at having to have this pointed out to me by a young child - out of the mouths of babes, etc.