1. A method, in a data processing system comprising a processor and a memory, for relational context sensitive anonymization of data, comprising: receiving, by the data processing system, a request for data, wherein the request specifies a relational context corresponding to a selected group of selected persons selected from a global group of persons based on the relational context, and wherein the relational context specifies one or more attributes of selected persons in the selected group that establishes a relationship between the selected persons and distinguishes the selected persons from non-selected persons in the global group that are not in the selected group; determining, by the data processing system, for the relational context corresponding to the selected group, based on a corpus of personal information data corresponding to the selected persons in the selected group, one or more key attributes in the personal information data; determining, by the data processing system, a rarity value for each key attribute of the one or more key attributes within the relational context of the selected group; and anonymizing, by the data processing system, selected key attributes in the one or more key attributes based on the determined rarity value for each of the key attributes within the relational context of the selected group, wherein determining the rarity value of each key attribute of the one or more key attributes comprises generating a relative rarity matrix data structure that identifies the one or more key attributes and their corresponding related relative rarity measures.