They had felt they were the opposite sex trapped in their bodies.
One family has redefined their lives together as parent and child after transitioning to opposite genders.
Watch: Transgender Sisters Share Their Story of Coming Out Together
Father Eric Maison and daughter Corey Maison, 15, used to be mother and son.
Corey Maison, 15, who loves mascara and lip gloss, was born a boy.
“I always wanted to be a girl,” she said. “I was very girly when I was younger.”
Corey is one of five and her mother, born Erica, never felt comfortable in her female body. Erica transitioned to Eric.
“I definitely felt like I identified with boys but I didn't actually realize it was possible I could become one,” Eric told Inside Edition.
It wasn't until four years ago, when the two watched a TV special on transgender teen activist Jazz Jennings, that everything became clear.
“I said, ‘Wow, I’m just like her. I'm a girl trapped in a boy's body’,” Corey admitted.
Corey started taking puberty blockers at 11 to stop facial hair growth and the deepening of his voice.
“Just seeing her courage and bravery in the face of so much adversity, I think that's what ultimately gave me the courage to come out myself,” Eric said.
For Eric, the transition began with a short haircut. Then, the 39-year-old started injecting testosterone.
“My voice has gotten deeper, I’ve grown facial hair even though I shave it, more body hair, leg hair and my muscles are getting bigger,” he said.
Read: Caitlyn Jenner Talks Dating After Transition: 'I Just Have a Lot of Friends'
Earlier this year, Eric had a double mastectomy.
“I felt like I was trapped in a woman's body and just that mastectomy made me feel free,” he said.
The transition has proved challenging for Les Maison, who is Corey’s father and Eric’s husband.
“It's difficult because I married this beautiful woman but I’m getting the opportunity to see someone become who they truly are,” he said.
As prom season looms across America, Corey and her family went and picked out a dress for the teen.
Her sister Ellen believes she will become prom queen.
Watch: 90-Year-Old Veteran Receives Honorary Diploma After Dropping Out to Fight in World War II
