She was born at Eltham Palace in Kent on 16 August 1355, the only child of Lionel of Antwerp, 1st Duke of Clarence, and Elizabeth de Burgh, 4th Countess of Ulster.

[2] Her father was the second son of King Edward III of England and Philippa of Hainault.

Philippa married Edmund Mortimer, 3rd Earl of March, at the age of fourteen, in the Queen's Chapel at Reading Abbey.

[2] Her cousin, King Richard II, remained childless, making Philippa and her descendants next in line to the throne until his deposition.

In the Wars of the Roses, the Yorkist claim to the crown was based on descent from Edward III through Philippa,[4] her son Roger Mortimer, and granddaughter Anne Mortimer, who married Richard of Conisburgh, 3rd Earl of Cambridge, a son of her uncle Edmund of Langley, 1st Duke of York.