Webservice or SQL : Master Customer Account Details after account merge

Summary:

We are running the customer merge at customer account level. e.g we have a Customer A, Customer B, and Customer C, and because of the similarities between Customer A & B both these customers got merged with Customer C. Now Customer A & B are inactive and only Customer C is valid and in the Active status.

Till the time of the merge process, customers A & B are having some invoices & orders associated with them, and since they are inactive because of the merge process , We need to use the customer C (as it is active now) to create a receipt. I need a help to know if we have any Webservice or SQL available to get the final(master) customer account(Account C) based on customer account A or B on the receipt.