Do i need a membership?

So if I get myself a CD of Rainbow Six Siege for the XBOX…
Does this require Xbox Live Gold?

Since Rainbow Six is a multiplayer only game, you will need Xbox Live to play it.

However, with a view to the questioner's writing skills, I wonder whether he is even allowed to play such a game because of his age. 😉

Yes, regardless of whether you bought a CD or in store, you need Xbox Live Gold to play online.