As of now Roger has the highest number of “confirmed” Conqueror’s Haki users in his crew: Gol D. Roger himself, Silvers Rayleigh, Kozuki Oden and Shanks.
Rocks D. Xebec is close second with 3 “confirmed” Conqueror’s Haki users in his crew: Big Mom, Kaido and Whitebeard. Anyway it’s almost guaranteed that Shiki the Lion and Rocks D. Xebec himself possess Conqueror’s Haki as well. So we should have at least 5 Conqueror’s Haki users in the Rocks Pirates crew.
Anyway, if Douglas Bullet is canon then Rocks Pirates and Roger Pirates would tie with 5 Conqueror’s Haki users each.
Among the Yonko crews, Big Mom Pirates have only 2 Conqueror’s Haki users.
The Whitebeard Pirates had 3 confirmed Conqueror’s Haki users: Edward Newgate, Portgas D. Ace and Kozuki Oden. Marco likely doesn’t have it or he would have used it at Marineford.
We still don’t know enough about Shanks, Blackbeard and Kaido’s crews.
Which brings me to the Straw Hat Pirates. Do you think they’ll surpass Roger Pirates/Rocks Pirates’ record? Will the Straw Hats have just 2 Conqueror’s Haki users like the Yonko standard? Will Luffy and Zoro be the only Conqueror’s Haki users in the Straw Hats crew?