ABC News' Felicia Patinkin reports:

Joshua Biyoyouwei has sickle cell anemia.

When he was just 20 months old, Joshua, now 6, had a severe stroke that left him with weakness on the right side of his body.

To prevent future strokes caused by the disease - a hereditary disorder that causes misshapen red blood cells resulting in a severe lack of oxygen - Joshua has been going to the Children's Medical Center Dallas to get blood transfusions every month for most of his life.

According to Dr. Timothy McCavit, the pediatric hematologist treating Joshua, a transplant is the only cure for Joshua's disease.

Robin Roberts' Journey: My First Birthday

"These blood vessels in his brain where his stroke occurred have continued to narrow," McCavit said. "We believe the transplant really offers him the best chance to not have a life-threatening stroke."

Between doctors' visits, Joshua is like most of the children in his age group. He loves to play, and likes football and basketball.

He manages his treatment with good humor and poise that are way beyond his years.

"I think Joshua has a huge heart," said Shelley Bernhard, a nurse. "You know, the things that we have to do, sometimes, are not the most fun. Starting an IV, having to sit in a chair for four hours but, I mean, he just loves it when you come in the room, loves the interaction."

Twenty percent of the people who are in need of bone marrow transplants are children, according to Be the Match, an organization that connects patients with donors and offers support, education and guidance before and after the transplant.

Joshua has been looking for a bone marrow donor match for four years.

His mother, Vera Johnson, knows in her heart that there is a match out there for her son.

Hoping to broaden the search, Joshua's family sent a YouTube message to "Good Morning America" co-anchor Robin Roberts, who underwent a bone marrow transplant two years ago after being diagnosed with myelodysplastic syndrome. Luckily, her sister, Sally-Ann Roberts, was a perfect match.

Most people aren't so fortunate. In fact, 70 percent of people who need bone marrow transplants don't have a match in their family, according to Be the Match.

Roberts has since spearheaded an effort to increase blood marrow donations through a public awareness campaign with Be the Match, inspiring more than 65,000 people to join the Be The Match Registry.

Click HERE to find out more about Be the Match and how you can help.

Joshua's family asked Roberts to make a plea to help Joshua find a donor.

"Robin, many people listen to you," Johnson said in the YouTube video to Roberts. "Have a voice for us to find a match for Joshua or kids like him."

"Please help me find my match," said Joshua.

The test to become a bone marrow donor includes just a simple swab of cheek cells. Hundreds of Roberts' colleagues at ABC News and her friends and family joined the Be the Match registry after her diagnosis, and Roberts hopes others will continue to get tested, and perhaps be a match for Joshua.

Joshua's family hopes their son will be able to find a match and live a full life.

"My dream for Joshua is being healthy, being able to just do what he loves to do," Johnson said. "Right now, Joshua feels like he can do anything - but to actually do it, it would bring joy to him and to me."