I'm not sure if this is an existing theory or not but in chapter 907 we learned that there are many in the Donquixote family who are leading normal lives. It is possible that Doflamingo's family was not the first in the Donquixote line to leave the celestial dragons and the others who left (perhaps even shortly after the void century) changed their names to D in order to hide their identities. When Homing left, his name got him killed, which is proof that if any Donquixote family members left in the past, they would have had to eventually hide their identies. This could explain why Dragon has such a grudge against the celestial dragons/world government and the reason he was able to empathize with Sabo at gray terminal. I think that many top officials of the world government know of the meaning of the D as well as many top tier pirates (WB, Shanks, maybe Rayleigh, etc..), and is the reason the government is so fearful of those who bear the D, since the government knows how much trouble they can cause. When Doflamingo was in chains on Tsuru's ship he said ' The family of "D." have been hiding in the shadow of history.' Shortly after he says the celestial dragons will be dragged down. Firstly, he doesn't call it the family of the "D.", he calls it the family of "D." implying that it is an actual family, not just a group of people, linked by the D. Secondly, I think when he says the celestial dragons will be dragged down, he is referring to the family of D, who hold both the power and status needed to bring down the celestial dragons. Not only this but i'm assuming most, if not all bearers of the D, have or will have the "will" to take them down once they discover the truth. Perhaps this is even what it means to have the "will of D". Edit: I think its also incredibly strange that both Homing and Corason died with smiles on their faces(Chapters 766 and 767). I'm not sure exactly how many people we have seen die smiling in the series but i cant think of any that weren't in the clan of D. Either way, I feel this is strong evidence to suggest that the Donquixote family is at least part of the D clan. What do you guys think?