Transcript for Dad and daughter transition together from mother and son
here with an extraordinary family drama. It involves a mom in Detroit with a transgender daughter. While watching her boy transition into a girl, this mother says she realized that Slee was, in fact, a man. So this is now a household with two transgender family members and they say at the heart of this family is a marriage that is growing stronger. Here's my "Nightline" co-anchor juju Chang. Reporter: At just 15, Cory mason's bravely sharing her transition from male to female. I feel like a princess. Reporter: She made this video to combat bullying and it went viral. I know what I'm doing, and I feel like it's the right thing to do, stop and help people. Reporter: Now she and her family are sharing more of their personal journey with the public. Cory's mother transitioning too from Erica to Eric. After a lifestyle of living as a woman, marrying and having five kids, Eric began his transition a year ago. I will never forget the first Joseph hormones that I took, it was like this overwhelming sense of calm and peace just came over me that I had never experienced in my life. I was like, wow, this is what Normal feels like. There's me and mom. Reporter: Eric says he was inspired by his own daughter's bravery. And for almost two years now, the two have been sharing their transition from mother and son, to father and daughter. So you two draw inspiration and support from each other, don't you? What was it like watching her walk this walk? Just seeing her and her bravery, just gave me the strength and courage to come out as well, and face the world as my true self. What goes through your mind when you hear Eric talk about you as a hero to him? I feel like I've done my part and helped him through his journey as he's helped me. That, I think, was probably one ever the hardest things too. All my friends would tell me, you're so beautiful, you have this beautiful body, I would kill for your body. I'm like, I would kill for not this body. Reporter: Just four weeks ago, Eric unchdr underwent a double mastectomy. I was overcome with emotion. I didn't expect for it to hit me that hard. I was like, there I am, that's me. This can't have been easy on your marriage? At first, I think the biggest struggle was top surgery, for my husband, especially. Because he loved my body. As much as I hated it, he loved it. And at first, I think he struggled with it, but he said, this is what will make you happy. So who am I to keep your happiness from you? Reporter: It was Eric who encouraged Corey to find her happiness, which is on clear display in this video, when she received her first dose of hormones. Do you know what that is? Reporter: True emotion, garnering more than seven million views. Do you know what that is? The day you started hormones. First day of my life. Why? Because that's when I started to transition as a female. I could proceed with what I would like to do. What's the best part of being a girl for you? Dressing up in heels, dressing and going to dances. Reporter: But she says the life changes have been anything but easy. Some of her peers taunted her. I would get spit on and shoved, called names. One person told me I should just go and kill myself because -- Oh, I'm sorry. He said that no one would miss me in this world. And that I shouldn't be here, there's no place for me to be. Reporter: But she didn't let it stop her. Last year, Corey's transgender anthem gaining more than 300,000 views on YouTube. Raising awareness against bullying, something she says she's experienced plenty of. She said she was inspired by another transgender girl, jazz Jennings, the now reality star, one of the youngest girls to have transitioned publicly. She spoke to ABC's Barbara Walters. There are some transgender children that have not been able to be transgender. And even want to die. I want to help those kids become the person they are. We watched a video of jazz Jennings, and I told my mom, I'm just like her at the end. I realized that oh my gosh, this is also me as well, but I can't think of that right now, I have to focus on my daughter. Reporter: It was so important for Eric to be supportive of his daughter, because Eric himself struggled in silence for decades, trying to come to terms with his own identity. It was difficult for me with my parents. I said, mom, I'm just like Corey, I was born basically in the wrong body. And she said, how come I never saw this when you were a kid? I said, mom, if you remember the fights we had and the things I asked for on my Christmas wish list. And she said, oh, I guess that makes sense. Is that repression, is that denial? I think it's denial. In that generation. It is a fair question, how could you not have known? Because I was not educated on what being transgender meant. If they would have said, this is what being transgender means, you're born with this anatomy and your brain does not identify with that, I think a lot of years ago I would have made that connection. Reporter: Today 1.4 million adults identify as transgender. But 18 to 24-year-olds are more likely to go public than their older counterparts. What's unclear is how common it is for two people in one family to transition. Dr. Lauren Schecter performed Eric's mastectomy, he specialized in the gender confirmation surgery. In my practice, this is the first time that I've cared for a parent, or I should say a family who's got both a parent and a child who are transitioning. What I think is unique to some degree for Eric and their family is the supportive nature of the family. Reporter: Despite transitioning, Eric says his kids still call him mom. I think that mom is an earned title. I feel like I gave birth to them, I nurtured them, I comfort them. I'm there for them and have been. I feel like, you don't necessarily have to be female to be mom. What's it like to watch Eric go through that transition? It was very cool, but there was kind of a sense of loss a little bit too. Reporter: Eric's husband says having a spouse transition raises a lot of new questions. Number one, for me, does this make me gay? No. Does it mean anything between my spouse and my thing as far as our relationship is concerned? No, it doesn't. It made it better. Reporter: He told me that Eric's transition has ultimately strengthened the marriage. A lot of spouses might think, this is is a deal breaker for me. But for you it isn't? It's not about the shell that you walk around in, it's about the person that you are, it's about the person that I fell in love with ten-plus years ago. And because that person now presents themselves in a different way, doesn't change how I feel. My husband is truly an amazing soul. Looking at my life now and the blessings that I have, five beautiful children and a beautiful husband, I think if I could do it again, I would not do anything differently. What does it mean to be comfortable in your own skin, in your own body? I can be who I want to be, inside and out. And I can show the world that no matter what, I can do this without you or with you. Reporter: For "Nightline," I'm juju Chang in new Baltimore, Michigan.
This transcript has been automatically generated and may not be 100% accurate.