Castlehaven, whose date of birth is unknown, was born into an well-known Anglo-Irish Catholic family with a history of military service and loyalty to the English crown. His father eventually took the oaths to William III and his seat in the Lords. In August 1700 Narcissus Luttrell‡ noted that the son had recently returned from ‘travelling beyond sea at his majesty’s charge’.
In March 1705 Castlehaven was listed as one of those Catholics licensed to bear arms in Ireland.
In 1716 Castlehaven was mentioned in Jacobite intrigue.
