Gordon Melniz is the first member of the Melniz family mentioned in the ASA storyline. He is introduced as a satellite customs officer in the story Of Money and Monsters. In the story, he aids Harry Edwards in erradicating a nasty lab-made bug that has taken up residence on the ship.
Goron Melniz is not in any other stories or mentioned again anywhere in the storyline. His grandson (Shane Melniz) does mention having a grandparent from Earth, but doesn’t clearly state this as being Gordon Melniz.