Redhboy,
I have the same question. I saw the program from the start and there was no indication given as to whether he was a relative or not. At first I was wondering why he was on the show at all, as I wouldn't have known him to be a historian.
But compared to the photographs and archive film the resemblance between him and O'Higgins was striking. Although the photographs and film in the documentary were all black and white as far as I am aware O'Higgins had reddish hair ... just like Damien Kybird.