Branko Chen was the grandson of Mavic Chen.
When the asteroid Maleficent was due to collide with the planet Uranus, it was sabotaged so that it would collide with the Hub. Chen and his followers hoped to seize power in the aftermath of the Federation's communications being knocked out. When his plan failed due to the intervention of the Seventh Doctor, he tried to escape in his Spar but was arrested by his own Technix. (PROSE: Uranus)