Okay I found the solution.
Reference material : How to Create Contact,Phone, Email under Communication tab for Customer Account Site using API [ID 985500.1]
Repeat Run --3. Create a physical location with customer account site level Address (ie, Specific contact address details). Note down x_location_id value
GET "x_party_id: " from "--8. Create a relation cont-org using party_id from step 7 and party_id from step 2"
Now Run "--4. Create a party site using party_id from step 2 and location_id from step 3" passing "x_party_id" from Step 8 & x_location_id from Step 3
Commit the changes and you will able to populate the account site specific contact person details