One device showing as two on WiFi network page

Last night my husband was trying to setup a booster. After connecting his iPhone to the booster, disconnecting from it, and then reconnecting back to our wifi, our xfinity network sent me a notification saying that a brand new iPhone had just connected to our network. Now when I look at the devices on our network, I see his previous Iphone information listed as well as an entirely different iphone (different hostname and MAC address). We basically now have two devices listed for what should be one… Unless it’s somehow possible that someone magically managed to log a new device onto our network at this exact moment without our detection?