Hi,
In SAP standard process in relationship data you are allowed to maintain Telephone, fax, and Email address field for the contact person. Rest of the relationship details it gets from the main account.
You can use BAPI_BUPR_RELATIONSHIP_CREATE/change to modify or create relationship data , here pass relationship category "BUR001" for contact person.
and to update the data in contact person main address you can use BAPI_BUPA_ADDRESS_ADD/change with role "BUP001"
Regards,
Neeraj