EXCLUSIVE: Christopher Reeve's Son Remembers His Late Father's 'Fierce Determination'

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.