How to get document owner to send custom mail template?

Hello,

I am trying to send custom template to Master agreement owner using below script:

ownerRef = doc.getDocumentOwnerUserReference();

owner = IapiAccountLocator.lookup(session, ownerRef);

email = owner.getEmail();

but system sends mail to agreement template owner always.

Any suggestion to findout Master agreement owner..

Regards,

Jagadeesh