Transcript for A 12-year-old boy and his real-life superhero meet for the first time on 'GMA Day'
celebrate people who do incredible things. Here is one guy who is at the top of our list. Take a look. My name is Ben trotter. I was a freshman at Rutgers. I mean, it's a little hard to remember. It was over 20 years ago. Reporter: One day Ben decided to donate blood. On the form he checked the box to be put on a bone marrow registry. At the time I didn't think about it. I went through college and got married, had children. Reporter: But more than two decades later in the fall of 2015, Ben got a call. A 9-year-old boy needed a stem cell donation. Ben had a decision to make. One of the doctors contacted me, and they spoke to me about if this doesn't happen, he could die. I don't know who this boy is. I don't know where he is. I have a son just a couple years younger, and I realized, wow, if my son was in this situation, if my son -- if my son was having this issue, I would hope that somebody would step up to do this. Ben was all in but would need to endure days of painful medications to prepare his body. This is definitely harder than I thought. Reporter: His wife was there comforting him on donation day. You will save a life and we will go home. Reporter: The very next day, his stem cells found a new home in a boy named Braylen. Braylen was born with sickle cell anemia, a debilitating and life-threatening disease. The same disease that took the life of his mother when she was just 27 years old. He's now being raised by his aunt and uncle. Sometimes we were in the hospital for a week or two then we would be home for another week to go back and do the same thing over again. Reporter: It's a time Braylen now 12 doesn't like to talk about. I had to go to the hospital a lot because I used to have lots of pain in my leg or my arm. Reporter: But they soon learned about a life-saving procedure through new york-presbyterian hospital. Typically the best case scenario is having a full sibling. Because Braylen was the only child and his mom passed away, that was not going to be an option, so the next best thing was an unrelated donor. Reporter: As fate would have it, the date Braylen received the anonymous donation fell on the anniversary of his mother's passing. That was a very comforting moment for us. Reporter: Braylen is now completely cured, and he has the dance moves to prove it. He sees that he now has that freedom and now is able to go out and play with his friends. I think it will take a few more years until he really recognizes his life expectancy has doubled now. Reporter: Braylen has a simple message for Ben and all the family and doctors that helped him through it. Thank you. Reporter: And this powerful lesson. Even if you don't know the person, you could still help that person. Ben is an example of a real-life superhero. Someone that people should be able to look up to and say this is how you actually go out and save a life. Wow, what an incredible message, and we're joined by Ben trotter, the man who donated his stem cells and saved Braylen's life. Ben, thank you, man. Thank you, thank you, guys. Ben, I find this so emotional to see the reaction of the family. I can only imagine how it makes you feel. Oh, Michael and Sara, I'm just so happy, so relieved to know that all the pain and stress this family went through, that it's over and that I was able to be part of them getting to this point. You know, it's indescribable, the feeling. You have never met Braylen or his family in person. No, no, I never got to meet them. You know, it's something I've always wanted to do. Well, are you ready? Yeah. Of course, I'm ready. Well, Braylen is here with his uncle and ounce. The whole family is ready to meet you guys. Come on out. Hey, Braylen. Braylen. That was some amazing flossing. That was something to be seen. I just learned recently. Hi. Hi. Hi. Hi, guys. Come on in here. Crowding. Hi. Yes. Come on in here. Let's squeeze. Oh, man. Look at those faces. How are you doing, Braylen. Good. I mean, you floss like nobody's business. That was impressive. What would you guys like to say to Ben now that you're getting to meet him in person? Thank you so much from the bottom of our hearts for saving Braylen's life and really doubling his life expectancy. You're welcome. I am glad I could be there and glad we've gotten to this point. I really am. Thank you from my heart. It was a nice time. And how is Braylen doing now? Braylen is doing amazing. He's 100% sickle cell free. Oh! And what you did was super selfless and really a true superhere react, especially for Braylen it would have been difficult to find a match as there is a lack of diversity in the bone marrow registry so thank you for everything you've done for us. You're welcome. Guy, I'm glad I could be there and like you said, you know, minorities, people of mixed race, they're underrepresented and, you know, it just takes, you know, checking off that box and a little more than that and willing to get to the end but it's so worth it. I'm so happy. Thank you. So we are so inspired, Braylen, by your strength, and you've been through so much so we wanted to do something special for you, so we are sending you and your family to Disney world. Thank you so much. That's awesome. Thank you. Thank you. And, Ben, you were so selfless and so courageous, we're going to send you and your Framily to Disney world too. Oh, my gosh. That is crazy. Wow. Everybody goes to Disney world. Disney world in Florida where there is more to see, do, taste and experience than ever before. You can visit all four not to be missed theme parks and starting in January, new limited time magic. Join in the celebration happening now only at the Walt Disney world resorts. I got to say this is like such an incredible story, and it represents everything that's right in the world. So we're so happy. Thank you so much, Ben. Braylen, we're happy you're well, my friend. Could you show us a little bit of that floss?
This transcript has been automatically generated and may not be 100% accurate.