The young hangers on are the fledged young that just don't want to leave the nest. Once they are flying and hunting sometimes they have a hard time letting go of the parents and keep coming back to the nest. The parents will finish off destroying the nest to remove the fledglings "home". The parents will sometimes just take off and leave the young who keep coming back to the nest. Last year they didn't need to kill the nest so there is still a good amount of it left in the tree for this round of laying/hatching.