Paired wifi devices appear as ethernet connections

[Gigi961]

Hi there 

My paired devices appear as ethernet connections without me physically connected them through ethernet on my broadband. How is this possible? Is it a hacking thing? 
I did found a few weeks back a LAN connection (with a Mac address that does not identify into anything) in my event log without me actually connectIng anything. I also have 2 unknown devices on my broadband as offline devices with again only MAC addresses that to not identify into anything specific. One of them has an IPv4 address 10.100.100.1 if this is helpful! These 2 devices they have come back after 2 factory resets as offline devices when all my other devices have been deleted. 

Any help and explanation will be appreciated a lot

Thank you for your time and energy

Thanks for your time and energy

[XRaySpeX]

@Gigi961 : Do you have any WiFi extenders? If so, are they connected to the router by Ethernet?

[Gigi961]

Hi there thanks for the reply! We do not have wifi extenders anywhere at home!

[XRaySpeX]

Which EE BB plan are you on including its speed? What EE router do you have (read label or post a pix)?