Alexandra and Matthew Reeve both serve on the board of the Christopher Reeve Foundation, which Reeve established to fund research for therapies and a cure, People magazine reports in its Nov. 13 issue.
"Our dad's accident really did connect us to this community: 4 million people in the U.S. who are suffering from paralysis," Alexandra Reeve, 22, tells the magazine. "We understand how important it is not only to find a cure but also to improve quality of life."
She and brother Matthew will join their half brother, Will Reeve, 14, at the foundation's annual gala on Nov. 6 in New York.
Christopher Reeve was paralyzed in 1995 in a horse-riding accident. He died in 2004 at age 52. His wife, Dana Reeve, died of lung cancer earlier this year.
Asked about her half brother, Alexandra responded, "Will's doing well. He loves school. He is playing hockey and football and keeping busy with friends."