Butler was the son of Sir Edmund Butler by the Honourable Eleanor Eustace, daughter of Rowland Eustace, 2nd Viscount Baltinglass.
Horatio Nelson, 1st Viscount Nelson | Viscount | Vickers Viscount | Bernard Montgomery, 1st Viscount Montgomery of Alamein | William Howe, 5th Viscount Howe | Charles Lennox, 2nd Duke of Richmond | viscount | Kelly Rowland | Robert Devereux, 2nd Earl of Essex | Hugh Grosvenor, 2nd Duke of Westminster | Garnet Wolseley, 1st Viscount Wolseley | Edward Harley, 2nd Earl of Oxford and Earl Mortimer | 2nd United States Congress | Rowland Hill | Charles Lyttelton, 10th Viscount Cobham | William Slim, 1st Viscount Slim | Michigan's 2nd congressional district | Edmund Allenby, 1st Viscount Allenby | 2nd | William Petty, 2nd Earl of Shelburne | William Lamb, 2nd Viscount Melbourne | Hugh Percy, 2nd Duke of Northumberland | Rowland Hill (postal reformer) | Julian Byng, 1st Viscount Byng of Vimy | George Villiers, 2nd Duke of Buckingham | Alan Brooke, 1st Viscount Alanbrooke | William Waldorf Astor, 1st Viscount Astor | James Bryce, 1st Viscount Bryce | Henry St John, 1st Viscount Bolingbroke | Henry John Temple, 3rd Viscount Palmerston |
He was the son of Sir Thomas Eustace (1480–1549), 1st Viscount Baltinglass and Margaret Talbot, daughter of Sir Peter Talbot of Malahide Castle, County Dublin.