When Jo Hirst's son told her he was transgender, she found there were not enough resources available to properly explain it to him.

So the Melbourne author decided to create one, in the form of a children's book: The Gender Fairy, inspired by her son.

'From the time he was 18 months old I think he had been trying to tell me in different ways that he did not identify with the gender he was assigned at birth,' Ms Hirst told Daily Mail Australia.

Jo Hirst is the author of The Gender Fairy, a children's book inspired by her transgender son

The books is about two children and a Gender Fairy, who helps them understand their identities

'For example clothing and there was about a 20 month period where he would not let us address him by his birth name he would choose different male names.'

'It was only halfway through prep last year, I could see his growing discomfort at having to go to school and be labelled a girl,' Ms Hirst revealed.

'Not long after his sixth birthday he finally came out and told me.'

The author said it was only then she realised how serious her son was about being born in the wrong body.

'He was insistent and nothing was going to relieve his distress apart from making a social transition to live as his true self.

'This involved choosing his name to suit his gender and living as the boy he really is, including at school.'

Ms Hirst decided to write the children's book when she realised there were limited resources for parents and their children

She said her family, community and her son's school have been nothing but supporting

Ms Hirst said she felt lucky that her family, community and son's school were all very supportive, but there was still a lack of information about the subject available for children and their parents.

'I soon realised that there was not a book I could read to my son about being gender diverse or anything he could take to school to help his peers understand,' Ms Hirst said.

'So I wrote him a book.'

She said a combination of growing up listening to the stories her father wrote for her and her siblings, and her background as a primary school teacher helped her with this process.

'I wanted to do something that would help all transgender children have the same support and understanding that we have experienced so I adapted the book to suit all children.'

The story follows two young transgender children who are guided by The Gender Fairy, a non-binary character who helps them realise and understand their gender identities.

Ms Hirst is pictured here with Evie, 10, a transgender girl who helped launch the book

Evie said in her speech: 'if she had been able to read this book in prep she would have had the words to explain herself to her parents sooner'

'It's written for young children because there are not a lot of resources out there for them. It's very simple and age appropriate with notes at the back for parents and teachers,' Ms Hirst said.

'Evie, the 10-year-old transgender girl who spoke at The Gender Fairy launch states in her speech that if she had been able to read this book in prep she would have had the words to explain herself to her parents sooner.

'Many transgender teens and adults have said the same thing to me. We need to give children the language to talk about gender,' Ms Hirst explained.

The author also emphasised that the topic is something that should be discussed from a young age, and hopes it helps transgender children understand they are not alone.

She urged parents in a similar situation to do their research, and praised The Gender Service at the Royal Children's Hospital for their ongoing support.

'Gender identity is not a taboo topic. It is not sexuality. They are two very different things. It's important that we support all children, including transgender children and gender fluid children.'