>> Again, are you both signed onto the same iCloud account? If you are, then you need to turn off iPhone Cellular Calls in the FaceTime settings on the devices. <<
Yes, we do have the same iCloud account. I ONLY use it for Contacts, and Find my iPhone. Nothing else. We have been sharing the same iCloud account for a long time, and never had this problem until I purchased the watch.
I read the link that you gave me. I'm still confused. I am not doing facetime, just regular voice calls.
I did this: Settings > General > Handoff & Suggested Apps, and turn off Handoff.
This did not help the problem, all three devices ring simultaneously.