The 2nd Earl's younger brother, Francis, studied at the University of Olomouc (Olmütz) in the Imperial Margraviate of Moravia, and served at the court of Emperor Ferdinand III as well as under Duke Charles IV of Lorraine, whose most intimate friend he became. He rose to be a Field Marshal in the Habsburg Army, having greatly distinguished himself at the 1683 Battle of Vienna and in the other Turkish campaigns, and was a member of the Order of the Golden Fleece. He was sent on many important diplomatic missions, and at the end of his life was Chancellor and Chief Minister to the Duke of Lorraine. Despite the Jacobite connections of his family, Francis Taaffe was confirmed as 3rd Earl of Carlingford by King William III, and the attainder and forfeiture of the estates incurred by his elder brother was repealed. This favour he owed to his position at the court of the Holy Roman Emperor, William's most important ally in the Grand Alliance.