The Grammy-winning rapper's 31-year-old sibling was diagnosed with the disease in 2001

Nelly’s sister Jackie Donahue, who suffered from leukemia and helped launch a campaign with her brother to find bone-marrow donors, died Thursday at a St. Louis hospital, the rapper’s publicist said.

Donahue, 31, was diagnosed with acute myelogenous leukemia in March 2001. The cancer was in remission for nearly two years before she suffered a relapse in 2003, after which Nelly (born Cornell Haynes Jr.) formed the Jes Us 4 Jackie campaign to find a bone marrow donor for his sister and to raise donation awareness.

Donahue’s family said in a statement they were “deeply saddened” by her death. “We are very proud of her efforts to educate and raise awareness about the disease and the need for African-Americans to join the National Donor Registry,” the family said.

Despite the efforts by the 30-year-old “Hot in Herre” rapper and his organization, a donor was never found for Donahue. Nelly himself was tested but was not a suitable donor. The pair were half-siblings who shared the same father, but they were raised separately. As adults, they became very close. When his sister lost her hair during a monthlong hospital stay during a round of chemo, Nelly cut his off too.

“Sometimes I call him crying on the phone, ready to give up,” Donahue, who was Nelly’s stylist before she was diagnosed, told PEOPLE last year. “He makes me think about positive things.”

In a statement from her family released Thursday they said of Donahue: “She will always be remembered for her loving spirit, energy and unshakable faith.”