Descendant of William Bligh edit

The National Portrait Gallery states that Jasmine Bligh is descended from Captain William Bligh, with no source or details. William Bligh's page has no references or links to the family of the Earls of Darnley. She is related to a *different* William Bligh (born 1775), but he is not the Bounty captain. Does anyone have unambiguous evidence that relates the two?