Currently http://build.fhir.org/relatedperson-definitions.html#RelatedPerson.relationship is defined as "The nature of the relationship between a patient and the related person", but it's not crystal clear which direction this works in.

Imagine we have Patient/123 representing a child, and RelatedPerson/abc representing that child's parent. Would the RelatedPerson.relationship be populated with "PRN", or "CHILD"? I believe the answer is "PRN," but the definition should explicitly describe this directionality. For example, we could update the definition could say:

"The nature of the relationship this Related Person has to the Patient. For example if the related person is a parent of the patient, the 'PRN' code could be used."