1. A multi-ownership tree-map visualization system comprising: a tree-map configured to visualize a set of interrelated nodes in which at least one individual node in said set is related to at least two parent nodes in said set; and, an event handler, executed by a hardware processor, programmed to process a proximity event associated with a specific portion of said tree-map by highlighting multiple portions of said tree-map in which said portions represent a single node in said set.