Christopher Reeve's oldest son Matthew Reeve tells PEOPLE at the New York City premiere of the documentary 'Super/Man: The Christopher Reeve Story' that his mother Gae Exton "is incredibly brave to tell her side of the story" of their family's history in the new movie.

Reeve's three children, Alexandra Reeve, Matthew Reeve, and Will Reeve, an ABC News correspondent, told "Good Morning America" on Wednesday at the premiere that the film is a tribute to their father's legacy and the lasting impact he had on who they are today.

Christopher Reeve's children Alexandra, Matthew and Will were a united front at the New York premiere of the documentary honoring their late father. See all the red carpet photos

The film could not have been made without the contributions of Reeve’s family, so it’s noteworthy when Reeve’s son Matthew opens up to the camera in the above, exclusive clip to discuss his favorite moment in his dad’s remarkable film career.

Christopher Reeve is the perfect Clark Kent / Superman, and no matter how hard any actor tries, no one will be able to bring to the character what Reeve brought to him. It was truly something special,

Will Reeve's mother died from lung cancer at age 44 in 2006, just 17 months after Christopher Reeve died at 52 in 2004