When the time comes, when suigetsu fight against Kisame, i think he will defeat him, plz don't make a discussion about the "why", thats another theme. I don't think, that kishi gives a charakter a dream or a goal for no reason. When, i say "when", he gets the samehada, means he is stronger than kakuzu.

But as mizu wrote, hawk was never really a big part from Akatsuki and even madara said, "you are fired", because hawk missed the capture of the hachibi

The sentence which confuse me is, a brother/sister from the hokage. It could only be complete new charakters, cause we never saw a brother/sister from danzou. Or Danzou would be himself, because he is the brother of Madara ^^, who is even still alive.

Which means he only took one of this brother eyes..... or both.... then replaced them....later on in hos life

Yeah something like that. The Thing is, in naruto there is no limit an impossible jutsus. All of us to know about the edo tensei from orochimaru. So, there is a chance that Madara resuscitated his little brother and snitched then the sharingan of Shisui.
But this question will be answered , when we get more about Danzous history, i think. His appearance was yet not really much, i remember only the story with nagato in the past, where he stood next to hanzo the Salamander.