OK Google, Call My Wife

Eventually, Google will automatically know who your wife is, your mom, dad, and maybe even your neighbor! Until then (or do they already), you can tell Google Now who these people are by assigning them a Google Now Voice Shortcut. You can view all your Nicknames under account Settings in your Android app.

To setup a Nickname, all you have to do is make a call using your voice. For Example, "Ok Google, Call my Wife"

Google will then ask who your wife is. Search for her and set it! Now all you have to do is tell Google To Call Your Wife.