User blog comment:Raptor of Love/Flamingos Cards/@comment-4899461-20130227173330

The club is Trébol. Apparently, the names of these guys come from the spanish words for the suits. And in chapter 695, it's said by Buffalo that Doflamingo was saving the "Heart Seat" for him.

Don't thank me, I just used the resources of the wiki to steal these ideas from others.