Grego was only six years old when Andrew Wiggin arrived on Lusitania. As a child, he showed a disturbing capacity for destruction, modeled on his "father's" habit of domestic violence, a temper which did not subside during later years. After Quim's death, he whipped a mob into a frenzy to attack the forest responsible, only to have them jump on the nearest one to hand—Human and Rooter's forest. After being chewed out by Valentine, Grego tried to end the massacre with as little bloodshed as possible, eventually placing himself between the surviving Pequeninos and his own riot. He later collaborated with Olhado on faster-than-light travel.