Lord Ardilaun was childless and the barony became extinct on his death in 1915. However, he was succeeded in the baronetcy by his nephew Sir Algernon, the third baronet, the son of Benjamin Lee Guinness, second son of the first baronet. As of 2014[update] the title is held by the third baronet's great-nephew, the fifth baronet, who succeeded his father in 2011. He is the grandson of the racing driver Kenelm Lee Guinness, grandson of the first baronet.
Arms of Guinness, Baronet of Ashford and St. Stephen's Green: Quarterly, 1st and 4th, Per saltire Gules and Azure a Lion rampant Or on a Chief Ermine a Dexter Hand couped at the wrist of the first'(for Guinness); 2nd and 3rd, Argent on a Fess between three Crescents Sable a Trefoil slipped Or (for Lee), with canton of baronet
Sir Algernon Arthur St Lawrence Lee Guinness, 3rd Baronet (1883–1954)
Sir Kenelm Ernest Lee Guinness, 4th Baronet (1928–2011)[1]
Sir Kenelm Edward Lee Guinness, 5th Baronet (born 1962)
The heir apparent is the present holder's only son Kenelm Arthur Lee Guinness (born 2005).
Guinness baronets, of Castleknock (1885)
Arms of Guinness, Baronet of Castleknock: Quarterly, 1st and 4th, Per saltire Gules and Azure a Lion rampant Or on a Chief Ermine a Dexter Hand couped at the wrist of the first, a crescent for difference (for Guinness); 2nd and 3rd, Argent on a Fess between three Crescents Sable a Trefoil slipped Or (for Lee), with canton of baronetsee Earl of Iveagh