ArcGIS Pro 2.8 API Reference Guide
RelationshipClass Class
Members 

ArcGIS.Core.Data Namespace : RelationshipClass Class
Represents an association between two tables in a geodatabase.
Object Model
RelationshipClass ClassRelationship ClassDatastore ClassRelationshipClassDefinition ClassFeatureDataset Class
Syntax
public class RelationshipClass : Dataset, System.IDisposable  
Public Class RelationshipClass 
   Inherits Dataset
   Implements System.IDisposable 
Remarks
The primary difference between a RelationshipClass and AttributedRelationshipClass is that a RelationshipClass does not have an intermediate table.
Inheritance Hierarchy

System.Object
   ArcGIS.Core.CoreObjectsBase
      ArcGIS.Core.Data.Dataset
         ArcGIS.Core.Data.RelationshipClass
            ArcGIS.Core.Data.AttributedRelationshipClass

Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

RelationshipClass Members
ArcGIS.Core.Data Namespace