As for the sixth dude on the far right there, we've no idea who he is (OBVIOUSLY Brian Epstein), but let's just see him as a the symbolic 'fifth Beatle' which a legion of others were rumoured to be.
Indeed, since news broke that producer George Martin had died (not Game of Thrones author George RR Martin, like some of twitter initially thought), a debate has been raging whether he was in fact 'the fifth Beatle'. Thankfully Paul McCartney has waded into the debate to confirm the title in a tribute he wrote earlier today.
Part of it reads: "He was like a second father to me. He guided the career of the Beatles with such skill and good humour that he became a true friend to me and my family... If anyone earned the title of the fifth Beatle it was George."
Safe in that knowledge, you can rest easy for the rest of the evening with the bona fide fifth Beatle.