Xfi app Showing Multiple Versions of one device as On WiFi. Explanation?

I named all of the devices using WiFi in our home on Xfi so that I can see which ones are using the most data and to monitor my kids’ usage. However, I’ve recently started noticing 2 or more versions of the same device (i.e. Joe iPhone X suddenly has Joe iPhone X-23 and Joe iPhone X-264) listed in the devices connected to WiFi. How is this possible when Joe only has one iPhone X? I have paused these phantom devices which do show different usage from the real iPhone X and they remain there until I am able to “forget this device.” That only happens when they are not connected though. Is someone hacking my wifi? Is a household member up to no good? Someone please explain how this can happen! And what to do about it. Thanks.