Connected devices are showing up multiple times

I have noticed that cell phones are showing up multiple times as connected devices under the xfinity app. Only 2 household members have iphones, however, sometimes 3 iphones are listed as connected. Today I am the only one home and it is showing 2 iphones connected to our gateway. My phone is connected to our 2.4 network. This unknown other phone is connected to the 5 network. Is this my phone connected twice or is this my childs phone showing up as still connected even though they have left the house with their phone? 

This has also happend with a older galaxy phone. Our gateway showed 2 phones connected all day, but the phone was taken from the house multiple times. Then it would show only one phone connected while this person was away with their phone. They came home and 2 phones were connected. The phone that stayed connected was on the 5 network. Again, I don't know if this is one phone showing up twice or are there two phones?