In 1827, Arbuthnott married in Kildare Catherine Maria ("Mary") Eustace (born about 1806 in Ireland; still alive in 1891 living in Sheepy Magna, Leicestershire, third daughter of Rev. Charles Eustace and descendant of the Viscounts Baltinglass.
In 1581 Cavanagh, alongside five others, was found guilty of treason for aiding in the escape of Viscount Baltinglass and refusing to acknowledge the English monarch as the head of the Church.
In the spring of 1548 he assisted the lord deputy in subduing a sedition raised in Kildare by the sons of Viscount Baltinglass.
Horatio Nelson, 1st Viscount Nelson | Viscount | Vickers Viscount | Bernard Montgomery, 1st Viscount Montgomery of Alamein | William Howe, 5th Viscount Howe | viscount | Garnet Wolseley, 1st Viscount Wolseley | Charles Lyttelton, 10th Viscount Cobham | William Slim, 1st Viscount Slim | Edmund Allenby, 1st Viscount Allenby | William Lamb, 2nd Viscount Melbourne | Julian Byng, 1st Viscount Byng of Vimy | 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 | Edward Grey, 1st Viscount Grey of Fallodon | Charles Bathurst, 1st Viscount Bledisloe | Walter Runciman, 1st Viscount Runciman of Doxford | Viscount Falkland | Samuel Hood, 1st Viscount Hood | John Anderson, 1st Viscount Waverley | James Craig, 1st Viscount Craigavon | William Beresford, 1st Viscount Beresford | William Barrington, 2nd Viscount Barrington | Stapleton Cotton, 1st Viscount Combermere | Rowland Hill, 1st Viscount Hill | Marcus Samuel, 1st Viscount Bearsted | John Monckton, 1st Viscount Galway |
He was involved in some military disasters, such as a defeat at Glenmalure on 25 August 1580 when Lord Grey led the troops (with Bagenal one of the commanders of the rear) into battle with Fiach McHugh O'Byrne and Viscount Baltinglass in the Wicklow mountain passes.
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.