A Very Unique Case : Delete Duplicate from Cross Referenced Table [Parent Child relationship]

Cross referenced table, i do not know if i am pronounce this is correctly or not. First see the table structure below, and let me know what this table is known as?, how to pronounce it? What is name of structure storing this kind of data.

XYZ
ID	CustomerID [Reference to Cus.]	RelatedCustomerID [Reference to Cus.]	Relation Ship of Customers
1	20021	20022	is children of
2	20022	20021	is father of
3	20023	20024	is friend of
4	20024	20023	is brother of
5	20025	20026	is children of

Do not forget to provide your inputs in comment section

Now the case is earlier the application is designed in way to hold the relationship between 2 customers in either way. Now as per new requirement this relationship are duplicate. We need to keep only 1 relation ship from cross reference rows.

example - 

1. Row 1 and Row 2 are duplicate, we need to keep only 1 row (any one)

2. Row 3 and Row 4 are duplicate, we need to keep only 1 row  (any one)

3. Row 5 is itself is unique

So did workaround with friends, of-course nothing is found on internet.google. Tried Differnt type of join , inner join , self join, min , max, dense rank, pivot but nothing works

Below is the query we prepared after all.

SELECT 
    distinct
    CASE
        WHEN CustomerID < RelatedCustomerID  THEN CustomerID 
        ELSE RelatedCustomerID 
        END AS CustomerID_v,
     CASE
        WHEN CustomerID  > RelatedCustomerID  THEN CustomerID 
        ELSE RelatedCustomerID 
        END AS RelatedCustomerID_V
FROM 
    XYZ
	 

This could be a good interview question as well