Who is the seventh Shichibukai?
The missing Shichibukai is Edward Weevil, who is introduced in chapter 802.


  Edward Weevil, or "Whitebeard Jr." is the self-proclaimed son of Edward Newgate and one of the Shichibukai. His mother is Miss Bakkin, the self-proclaimed lover of Newgate.He was first mentioned by Commodore Brannew in a discussion of the current Shichibukai ranks to several high-ranking Marine officers, but was not explicitly named until after Donquixote Doflamingo's defeat.