Born the only legitimate daughter of Rhys ap Tewdwr, the last King of Deheubart around 1085, Nest ferch Rhys had an equally tumultuous life as her sister-in-law, Gwenllian ferch Gruffydd, whose story is told here: http://www.historynaked.com/gwenllian-ferch-gruffydd/
Nest’s mother was a princess of Powys, another kingdom in western Wales. When the Normans invaded in 1066, William I only pushed as far as Offa’s Dyke. William made alliances with Welsh rulers, one of which was Nest’s father, and acknowledge the sovereignty of the Welsh princes. This all changed when William died in 1087. His successor, William Rufus, sent the Marcher Barons into Wales to take over. The tentative peace was broken. At a battle outside Brecon in 1093, Nest’s father was killed. Her younger brothers fled to Ireland, and she and her mother were taken hostage by the Normans.
As the last daughter of a Welsh king, Nest was an important hostage and taken to the court of William Rufus. There the fourteen year old beauty caught the eye of the king’s brother, Henry. Henry was a notorious womanizer and went on to have twenty illegitimate children. He charmed the young princess and they became lovers. She continued as his mistress even after Henry’s ascension to the throne of England in 1100. They had a son together, Henry FitzRoy in 1103.
Not long after the birth of their son, Henry had Nest married to the governor of one of his barons, Gerald de Windsor. Gerald was put in charge of Pembroke Castle, and his Welsh wife gave him legitimacy in the eyes of his Welsh subjects. Although Gerald was much older than Nest, it seemed to be a tranquil marriage and five children were born. In 1109, Gerald built a new castle Cilgerran and Nest and children went to live there. Nest was now in her 20s and a renowned beauty.
The rest of Wales was rebelling against Norman rule, and one of the main leaders of the rebellion was Cadwgan, the Prince of Powys. His son Owain had heard of the great beauty of the Norman lord’s wife and wanted to see it for himself. The fact they were second cousins didn’t stop him. Legend says that over Christmas of 1109, Owain attended a banquet and saw Nest for himself and was struck by her exquisite looks. That night, he and his men broke into Cilgerran Castle. Some stories say they scaled the walls, others say they dug a tunnel underneath them. What is known is they got in. The stories say Gerald escaped down a privy hole, but Nest and her sons were taken and the castle sacked. There is a great question mark as to whether Nest went with Owain of her own accord or was raped and kidnapped. Some stories say she was raped in front of her children, and others say she bore Owain two children during her time with him. However, there are no mention of these children in the Welsh genealogical records.
The Normans were outraged over her treatment. Her old lover, Henry I, offered the kingdom of Powys to anyone who would rescue Nest and avenge Gerald. Eventually, Owain released Nest’s children then Nest herself, but the damage was done. Henry bribed the other Welsh nobles to attack Owain and his father Cadwgan, and a civil war began. Owain eventually fled to Ireland. Eventually, Owain was lured back by a royal pardon ostensibly to help with the civil war. He was met with Gerald and a band of Flemish archers. Whether this was a setup from Henry or just happenstance is unknown, but Gerald made sure Owain was a pincushion.
Gerald died a year later leaving Nest a wealthy widow. She married twice again and had at least three more children. One of her sons from her later marriage was Robert Fitz-Stephen, who became one of the Norman conquerors of Ireland. Her grandson is the chronicler Gerald of Wales. It is said half of Wales can claim descendancy from Nest. She died in 1136.
Her story became popular in the 19th century and the Victorians called her the Helen of Wales. She was accused of dallying with Owain and encouraging his attack. Her relationship with Henry I prior to her marriage was all the proof the Victorians needed. Further story has cast doubt on the story she was abducted at all or if her dalliance with Owain was with her consent. As with most stories we will never know. However, this young woman left her mark on English and Welsh history.
Sources available on request