Coax cable for TV

I have been asked to connect the TV in my brothers new house but there are two coax cables connected together in parallel with the standard screw in adapters coming down from the aerial, do i just need an adapter and use one of the cables or do i need to use some sort of adapter and both cables.

(UK if it helps)

Labels on the connector. most likely a splitter.

its the one on the right in this image, he has satellite?

There should be two coax inputs on the back of your satellite box, no?

I have no idea about TV never used it i have only ever used online services, he said that it was digital but i take my guess that he has sat as correct then