Dear RK,
In your case who will be the Payer?
Since standard SAP creates Billing document for Payer.
And in case different sold to parties to be shown Invoice output, you can maintain a Table for main sold to party link to other sold to parties. And in output if the default sold to party is invoiced default other (ex - 2 soldto parties will also get Invoiced).
In standard,customer master partner functions - only one Sold to party in Partner function can be included.
And Default tick mark option is used for ship to parties. Hope if partner function procedure is explored you may get some more options.
Regards,
OD