He was the son of Drogo of Mantes, Count of the Vexin, and Goda, daughter of King Ethelred the Unready of England and Emma of Normandy. Thus, he was a nephew of the English Saxon King Edward the Confessor, who placed him in command of the Earldom of Herefordshire. He himself married a woman named Gytha.
When Godwin returned from exile in 1052, there was almost war between the English Saxons and the Normans, but it was prevented and many Normans had to flee the country. Edward the Confessor intervened on Ralph's behalf, for he loved him dearly. Godwin made peace with his underling Ralph, but died on September 14, 1053.
In 1055, Gruffydd ap Llywelyn, King of Gwynedd (and later all Wales), invaded Ralph's lands in Hereford along with the exiled Earl Ælfgār. Arming all his men as Norman knights, they sallied forth from his seat at Hereford Castle and were soundly defeated on October 24, 1055.
Gruffydd ap Llywelyn took Hereford and destroyed the new castle. Ralph was disgraced and he died two years later in 1057, never having recovered from the shock of loss or the ignominy of his defeat: he was ever after called the Timid, less for actual cowardice as for his trust in armoured cavalry over the traditional Anglo-Saxon war form.