How do I set who "my wife" is for Siri?

In my contacts, I have the "spouse" field filled in with my wife's contact information. In my wife's contact, I have the spouse field set as my contact information. When I tell Siri, "send a text to my wife," (like in the Siri demo video), Siri tells me that she doesn't know who my wife is... A coworker suggested I change either her name to "my wife" or the nickname field to "my wife", but I was hoping Siri would be able to figure it out from the spouse fields... Is that setting the bar too high?