Roughly 20,000 Americans a year need a bone marrow transplant, but only 2% of the population is on the national registry. According to the Gift of Life Marrow Registry, only about 30% of matches are family members. That’s why when Riley Martin was diagnosed with leukemia and started his search for a donor, his CrossFit gym members stepped up to the plate.

Health and fitness enthusiast Riley Martin could usually be found at the gym or outdoors before his recent diagnosis with acute myeloid leukemia. Now the 22-year-old from Amsterdam needs to find a matching bone marrow donor to aid his battle against cancer. Riley was diagnosed with acute myeloid leukemia, an aggressive type of blood cancer rare in young people, in February.

Blowing out the candles for a fourth birthday is a huge milestone for twins Mackenzie and Sloane Caston. "They’re beautiful, amazing girls, and they are so vivacious, and you know with Sloane, Sloanie is so resilient," Keri Caston, Sloane’s mom, told Ivanhoe. Born healthy, six-pound, bundles of joy, at eleven months Sloane was diagnosed with a rare brain tumor. Despite treatment cancer kept coming back in her spine, then in her blood.

Each year, more than 18,000 people, in the United States are diagnosed with life-threatening illnesses where a bone marrow transplant is their best treatment option. Thousands of those on the list are children. Only 30 percent have a matching relative, leaving many hoping for a stranger to save their life. One of those on the list, a little four-year-old who is on a mission to find a match.

When you meet 3-year-old Avery Cook, you'd never guess that when he was just 8 months old, he was fighting the biggest battle of his life. "We were actually on a family vacation during Christmas time," Avery’s mother, Bailey, said. A fun time turned somber quickly when bath time came around. "I sat in the tub with him...The way the light hit his back, you could see how bruised he actually was."

A truly altruistic act is often one done without the knowledge of others, such as donating blood to save the life of someone you will never meet, or donating one’s organs. Often these donations lead to life-saving treatments. One Spring Hill family, however, recently had the opportunity to meet with a bone-marrow donor that saved their 3-year-old son’s life.