Background
Fitzgerald was the second son of Gerald de Windsor, Constable of Pembroke Castle by his wife, Nest ferch Rhys, Princess of Deheubarth and a member of the Welsh royal House of Dinefwr.
Fitzgerald was the second son of Gerald de Windsor, Constable of Pembroke Castle by his wife, Nest ferch Rhys, Princess of Deheubarth and a member of the Welsh royal House of Dinefwr.
A Welsh Marcher Lord, Lanstephan fought under FitzMartin at the Battle of Crug Mawr in Wales 1136. Diarmait Mac Murchada (Dermot MacMurrough), the deposed King of Leinster who had been exiled by the High King of Ireland, sought Cambro-Norman assistance to regain his throne. Lanstephan participated in the resulting 1169 Norman invasion of Ireland.
He assisted his younger half-brother Fitz-Stephen in the Siege of Wexford (1169).