Matthew Reeve sat down exclusively with ET to remember his late father and share how he and his siblings carry on their dad's legacy.

"He had a fierce determination, a dedication to the cause and found himself in a position he might not have chosen, but he chose to embrace it," Matthew told ET at the 25th Anniversary of "A Magical Evening" for the Christopher & Dana Reeve Foundation on Thursday. "We grew up with him in a wheelchair and a spinal cord injury just doesn't happen to the individual it happens to the whole family and everyone's lives are affected."

WATCH: Christopher Reeve's Son on His Late Father's Legacy

Today, Reeve's kids, Matthew, 35; William, 23; and Alexandra, 32, are dedicating their lives to fund research to cure spinal cord injuries through the Christopher & Dana Reeve Foundation.

"My sister and I and now my brother are on the board of directors," Matthew said. "We're at this amazing threshold in research for the spinal cord injury community."

The late Robin Williams was a close friend of Christopher's and the comedian's 32-year-old son Zachary and ex-wife, Marsha Garces, attended the gala along with Meryl Streep and Meredith Vieira, to support the Reeve family. Matthew told ET that Williams had a big impact on his life.

WATCH: Robin Williams & His Christopher Reeve Connection

"I knew him my whole life and our families have always been very close," Matthew said. "Their relationship was more than a friendship. It was a brother hood."

Watch the video for more.