Zack and Tria and Golly

The first youth in Grabon’s nest was Golly, then Tria and last it was Zack. Golly was there knowing he would die there. Tria was a visitor, but she is so small and young that everyone makes room for her inside the nest. Besides, she befriends Golly, which pretty much means she hits everyone’s soft spot. Then Zack joins the party, half angry and all scared, he is rescued from a difficult situation. Little by little you see him fitting in, blending in and becoming a part of the clan. At the end of Healing, Golly dies, Tria is universally accepted and Zack is well on his way to straightening out his thinking and attitude. In book 5 the sibling like relationship between Zack and Tria develops. How do you think Grabon reacts to sibling rivalry?