Empire Poker IS or ISN'T skin for PartyPoker?

I'd like to know that for sure cause they offer rakeback and if the numbers are correct I'm giving away a lot of money (currently play at Party), but if they are the same room I don't see any reason why I wouldn't enjoy the same number of players for more money?

If they are not party poker skins do they have other room that merge into Empire "network"?

The same question goes for multipoker and Eurobet poker, are they party poker skins or stand alone rooms?

Thanks in advance for all the answers!