Hi,

FYI, all the TP-Link powerline adapters are compatible with each other. You can add another powerline adapter into the existing network. 

While cause the current one is TL-PA251 which is a little bit old, you can select the 4 series powerline adapters. 

Below is the instruction to pair them: 

https://www.tp-link.com/support/faq/258/

And you can exchange their positions to serve different devices.

May it help and have a nice day. 

Tudes24 wrote

I have 2 powerline adapters (model TL-PA251) happily paired for the last 5 years and now wish to add 2 more. I'm looking at 2 TL-PA4010PKIT adapters. Will these be compatible and what exactly would I need to do to add them successfully please? I'm thinking of using one to replace the older adapter serving the router and using the other for my son's Xbox. The one currently serving the router is as I said already paired with the other TL-PA251. Would I need to indevidually re-pair the 2 old ones and the other new one to the new one that would be connected to the router? 

Thanks