A three-year-old boy from Lancashire in the UK changed his gender from the age of 3 after being sent to live with foster parents, whose own son had recently transitioned at the age of 7.
A closed family court hearing in Preston heard that the couple's youngest foster child was sent to school dressed in girl's clothes despite teachers "expressly asking" the parents not to.
A third child previously fostered by the couple, named only as CP and TP, was found to have "gender identity issues".
Lancashire County Council's social services launched an investigation into the parents' actions after fearing they had "manipulated" their children's gender, "actively encouraged" the change and risked causing "significant emotional harm" to the young children.
These claims were dismissed by Mr Justice Williams, who found that "the evidence from almost all sources of how the children are prospering in the care of CP and TP provides very powerful support to the contention that CP and TP are good parents".
Fears about the children's "early transitions" of gender were expressed by some experts but the judge rejected these concerns after Harley St gender expert Vickie Pasterski said the children's gender dysphoria had biological foundations and had not been caused by any "interpersonal influence or environmental interference".
This view is not supported by experts at London's Tavistock centre, the gender identity development service of Britain's National Health Service.
The head of clinical psychology at the Tavistock, Bernadette Wren, wrote recently in an academic paper that "younger gender-atypical children are likely to be more easily influenced by their parents' view about gender, even to the point of assuming an absolute, long-term commitment to a binary gender identity and a social transition".
Another clinician at the Tavistock told the Sunday Times that to have two children of that age undergoing full social transition in the same family was "unheard of in my experience".
However, Justice Williams found that Pasterski "compellingly rebuts" the social services' claims and "that neither . . . have suffered or are at risk of suffering significant emotional harm arising from their complete social transition to females occurring at a very young age".
The findings of the hearing, published last week, detail how TP and CP had fostered children for 16 years.
Five children aged between 4 and 17 were the subjects of the court proceedings. Two of them are the couple's biological children and three are fostered.
Their youngest biological child, named as R in the report, transitioned from boy to girl at 7.
Her parents immediately took steps to legally confirm her new identity by ordering a new passport but R remained unhappy telling a member of staff at her school shortly after that "she did not think life was worth living".
After a boy, known as H, was placed with the family at 3 and was being dressed in girl's clothes before starting school, the mother, TP, was reported to have told a teacher: "Here's another one for the Tavistock."
When H started school the school requested that he attend dressed in a boy's uniform, but arrived in the girl's uniform instead.
Last July the council acted to remove the five children from the parents' care, claiming that TP and CP had "acted in a precipitate manner in relation to perceived gender dysphoria" and were "resistant to acknowledging any potential disadvantages to R and H of being identified as transgender prematurely".
Experts were appointed to review the case, with one independent social worker, Alex Sayer, noting "some concerns that CP's attitude to gender dysphoria might lead to faulty decision-making with good intentions".
Sayer said both parents "presented as closed to the prospect of either R or H reverting back to their assigned gender", which could "cause emotional distress" but agreed with Pasterski that the children should stay with the parents.
Lancashire council decided not to remove the children and Justice Williams made it clear that he agreed with Pasterski, saying the concerns had been "comprehensively dispelled".
While there are no official statistics on the number of trans people in New Zealand, at the Wellington Endocrine Service the numbers identifying as trans at their clinic shows an increase in recent years — from between 10 and 15 a year between 2000 and 2008 to 30 in 2014 and 92 in 2016.
The age ranges in 2016 were between 17 and 51 but most were at the younger end — the median age was early 20s.