Swift MacNeill
From Anecdotes about Nineteen Century Authors

John Gordon Swift MacNeill, Irish politician and jurist, was descended (as Mahaffy would have known) not from the unmarried Dean (Jonathan) Swift, but from his cousin Deane Swift, a son of Jonathan Swift's uncle Godwin, and the father of Deane Swift his biographer.

Note from Sir John Mahaffy, from Literary Anecdotes