Create Relationship

Right-click geodatabase and select New > Relationship Class.
Enter the name of the new Relationship class.
Select the Origin table or feature class.
Select the Destination table or feature class.
Click Next.
Select the type of relationship (Simple or Composite), and then click Next.
Create labels for the relationship, and then click Next.
Select a cardinality, and then click Next.
Add attributes to the relationship class, if necessary, and then click Next.
Select a primary key and foreign key, and then click Next.

IMPORTANT: Typically the ObjectID is used as the foreign key. However, if you're using Geodatabase Replication and have created GlobalIDs for your feature dataset, you need to use GlobalID as the foreign key instead of ObjectID.
Review the summary and then click Finish to create the relationship class.