Family's Category can't be changed because the Family contains Shared Parameters which are not permitted in the new Category.

public static FailureDefinitionId FamilyNoExternalParametersError { get; }

Public Shared ReadOnly Property FamilyNoExternalParametersError As FailureDefinitionId
	Get

public:
static property FailureDefinitionId^ FamilyNoExternalParametersError {
	FailureDefinitionId^ get ();
}