Mail merge one letter to spouses having separate contact entries?

I create separate contact entries for every individual (ie both my Mom and
Dad). This allows me to enter separate birthays, email addresses, cell phone
and work numbers, etc.

BUT - when I perform a mail merge, I get TWO letters. My desired result is
to have the merge say "John and Jane Doe" and to still have all of the info
on both contacts. I wonder if linking can help with this?

Help!