Elen ferch Llywelyn (c. 1207 – 1253) was the daughter of Llywelyn the Great of Gwynedd in North Wales by Joan, Lady of Wales, the natural daughter of King John of England.

Elen married John of Scotland, 9th Earl of Huntingdon, in about 1222. He died aged thirty in 1237, and she was forced by King Henry III (her mother's half-brother) to marry Sir Robert de Quincy, the son of Saer de Quincy. Their daughter, Hawise, married Baldwin Wake, Lord Wake of Liddell. Hawise's granddaughter, Margaret Wake, was the mother of Joan of Kent, the first English Princess of Wales. Source: https://en.wikipedia.org/wiki/Elen_ferch_Llywelyn

Helen ferch Llywelyn is the 22nd great grandmother of Cathy Truesdale.

∼Birth: c.1218

Elen was the daughter of Llywelyn the Great of Gwynedd in North Wales by Joan, Lady of Wales, the natural daughter of King John of England.

Elen married John of Scotland, 9th Earl of Huntingdon, in about 1222. He died aged thirty in 1237, and she was forced by King Henry III to marry Sir Robert de Quincy. Their daughter, Hawise, married Baldwin Wake, Lord Wake of Liddell. Hawise and Baldwin's granddaughter, Margaret Wake, was the mother of Joan of Kent. Joan of Kent was the wife of Edward, the Black Prince and the mother of Richard II of England, who was deposed and died without heirs.

The blood of Llywelyn the Great eventually came into the English royal family through Joan of Kent's earlier marriage to Thomas Holland, 1st Earl of Kent. By their eldest son, Thomas Holland, 2nd Earl of Kent, two of his six daughters were ancestress;

• Margaret Holland who was the mother of John Beaufort, 1st Duke of Somerset; John Beaufort was the grandfather of Henry VII.

• Alianore Holland was the grandmother of Richard Plantagenet, 3rd Duke of York. Richard was the father of Edward IV and Richard III and a grandfather of Elizabeth of York, queen to Henry VII.

By Thomas, 2nd Earl of Kent's other daughter, Eleanor Holland, Countess of Salisbury, Elen ferch Llywelyn was an ancestress of Queen consorts Anne Neville, consort of Richard III and daughter of Warwick, the Kingmaker, as well as Catherine Parr, the last wife of Henry VIII.