Hill, 19, was in the process of transitioning from male to female when she met Andrews, 18, who was undergoing his own transformation from female to male.
While supporting each other through these major life changes, the two teens fell in love. Now the former couple – they broke up earlier this year – announce to PEOPLE they're sharing their stories in two separate memoirs to be released Sept. 30.
"It's a story of acceptance, love, triumph and standing up when you've been knocked down," Andrews writes in a press release for his upcoming book Some Assembly Required: The Not-So-Secret Life of a Transgender Teen.
Andrews, who once struggled with bullying and low self-esteem to the point of considering suicide, writes that his book "gives me the opportunity to open the hearts and minds of those that just don't understand and inspire those that do."
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"There were many factors that caused Arin and me to break up – but arguably many of them were caused by the attention we were getting," Hill tells PEOPLE. "There was a lot of pressure on us to be together and to be happy."
Adds Andrews: "The breakup was more about needing to discover who we were becoming."
When it comes to their books, "The original idea was for Arin and Katie to write a shared memoir," their editor, Christian Trimmer, writes in press materials. "It quickly became clear that the world needed to hear their individual stories."
Despite the split, Hill tells PEOPLE, "We still understand each other better than anyone else ever will."
As for Hill's memoir, Rethinking Normal: A Memoir in Transition, she hopes it can be a tool for everyone.
"I don't want this book to just appeal to transgender people or their allies," she writes. "I want people to understand that there really is no such thing as normal."