Richard of Conisbrough, 3rd Earl of Cambridge (20 July 1385 – 5 August 1415) was the second son of Edmund of Langley, 1st Duke of York, and Isabella of Castile, Duchess of York. He was beheaded for his part in the Southampton Plot , a conspiracy against King Henry V .
Richard of York was born on 22 September 1411, the son of Richard, Earl of Cambridge (1385–1415), and his wife Anne Mortimer (1388–1411). Both his parents were descended from King Edward III of England (1312–1377): his father was son of Edmund, 1st Duke of York (founder of the House of York), fourth surviving son of Edward III, whereas his mother Anne Mortimer was a great-granddaughter ...
Mortimer's sister Anne de Mortimer married Richard of Conisburgh, 3rd Earl of Cambridge, son of Edward III's fourth son Edmund of Langley, consolidating Anne's place in the succession with that of the more junior House of York. As a child, Mortimer was not considered a serious contender and, as an adult, he showed no interest in the throne.
Anne de Mortimer, also known as Anne Mortimer (27 December 1388 – c. 22 September 1411), was a medieval English noblewoman who became an ancestor to the royal House of York, one of the parties in the fifteenth-century dynastic Wars of the Roses. It was her line of descent which gave the Yorkist dynasty its claim to the throne.
8. Richard of Conisburgh, 3rd Earl of Cambridge: 4. Richard Plantagenet, 3rd Duke of York: 9. Anne de Mortimer: 2. Richard III of England: 10. Ralph Neville, 1st Earl of Westmorland
She married secondly, Richard of Conisburgh, 3rd Earl of Cambridge, beheaded on 5 August 1415 for his part in the Southampton Plot.  Lady Elizabeth Neville, who married Sir Thomas Willoughby.
Family. Alianore Holland was born 13 October 1370 in Upholland, Lancashire, the eldest child of Thomas Holland, 2nd Earl of Kent, and Lady Alice FitzAlan, the daughter of Richard de Arundel, 10th Earl of Arundel, and his second wife, Eleanor of Lancaster, daughter of Henry, 3rd Earl of Lancaster, grandson of King Henry III.