Add a custom relationship and name the field what ever you want. Assign a contact to that relationship. Then use that alias when you want to send a message etc. i.e In your contacts it should look like this: Most Interesting Man In The World: John Appleseed You: Tell Most Interesting Man In The World Whats up! Siri: Here is your message to John Appleseed Note: this does not work with google sync or exchange sync since they both use the same technology "exchange sync" which does not support custom fields. But even if you do use those services you can still add an iCloud address book with a single contact. This will be your contact info, then add the custom relations to it. i.e Mom, Dad, Brother, Sister, Custom1, Custom2... You will also want to go into Siri settings and assign this contact as My Info.