Help blocking devices on my network

Help blocking unwanted devices

I have internet through xfinity and I need help blocking devices from accessing my network.

There are only 2 devices that belong to me and the rest (5) I assume belong to my neighbors who I apparently provide internet to.

I don’t know what they are doing or how they are doing it, but the devices are hidden and don’t show up on my router when I log into 10.0.0.1

I have the xfinity app, but they also don’t show up on there.

I have downloaded a few different apps and they found them.

Help me!