This is the ValueSet that contains all the codes in Defining Relationship Type Value Set (http://hl7.org/fhir/uv/termchangeset/ValueSet/defining-relationship-type-vs) and Defining Relationship Type Value Set (http://hl7.org/fhir/uv/termchangeset/ValueSet/defining-relationship-type-vs). E.g. what you have to deal with if you get resources containing codes in either of them