Alexandra and Matthew Reeve both serve on the board of the Christopher Reeve Paralysis Foundation, which the actor and activist 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 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."