Jonas and Nicole Maines are funny, charming and also strikingly attractive. With their dark brown eyes and quick smiles they look so similar you d think they were identical twins–except he s a boy and she s a girl. So that’s impossible, right?

Wrong. The Maineses, 18, were born identical twin boys and named Jonas and Wyatt. But by the time he was two, Wyatt made it clear he felt like a girl. He asked when his penis would fall off. He begged to be allowed to wear sparkly clothes and grow his hair long. Whenever we were playing dress up she always wanted to be the girl, Jonas remembers in an interview with PEOPLE. She always played with the dolls. Jonas always went along with it. I never questioned it.

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In a new book Becoming Nicole: The Transformation of a an American Family, Pulitzer-Prize winner Amy Ellis Nutt tells the honest, intimate story of how Wyatt became Nicole, including how their mother Kelly s certainty that she would do whatever it took to raise happy children overcame her fears, and how their father Wayne struggled to accept what Jonas always knew.

Where did Jonas’ understanding come from? Were he and Wyatt talking in some private twin language? Jonas is not a believer in that, but it was very natural for me, he says. It just made sense.

He protected Nicole (the family changed Wyatt s name just before fifth grade) fiercely, particularly in elementary school, where she was harassed and bullied until Kelly and Wayne decided to move three hours away (leading to a ground breaking civil suit establishing rights for transgender children). In middle school in Maine s largest and most liberal city, Nicole went stealth, telling no one she was trans. For years the family lived with the dread of being discovered and harassed again. Today they re breathing easier.

And this summer, just before college started, Nicole, who took first puberty suppressants and then female hormones as a tween and teen, had gender reassignment surgery. In her hospital room, with Jonas once again sticking by her side, Nicole told a friend one of the great things about having an identical twin: I can see I would have looked awesome as a man, too!