In 1352 Lionel of Antwerp 1st Duke of Clarence and Elizabeth Burgh Duchess of Clarence were married. He by marriage Earl of Ulster. She was the sole heir of her father and brought the de Burgh inheritance of the lands of Ulster to the marriage. As a consequence of their earlier betrothal he had been called Earl Ulster since 1347. She the daughter of William Donn Burgh 3rd Earl of Ulster and Maud Plantagenet Countess Ulster. He the son of King Edward III of England and Philippa of Hainaut Queen Consort England.
On 16th August 1355 Philippa Plantagenet Countess March 2nd Countess Ulster was born to Lionel of Antwerp 1st Duke of Clarence and Elizabeth Burgh Duchess of Clarence at Eltham Palace, Kent. At the time of her birth she was Heir to the Throne of England since her uncle Edward "Black Prince" was yet to be married.
On 26th February 1360 Roger Mortimer 2nd Earl March died. He was buried at Wigmore Abbey. [her future husband] Edmund Mortimer 3rd Earl March, Earl of Ulster succeeded 3rd Earl March, 5th Baron Mortimer of Wigmore.
On 10th December 1363 [her mother] Elizabeth Burgh Duchess of Clarence died at Dublin. She was buried at Clare Priory, Suffolk.
In June 1368 [her father] Lionel of Antwerp 1st Duke of Clarence and [her step-mother] Violante Visconti were married in the Church of Santa Maria Maggiore, Milan. The wedding festivities were lavish and ostentatious. The banquet, held outside, included 30 courses of meat and fish presented fully gilded. Between the courses the guests were given gifts such as suits of armour, bolts of cloth, war horses, arms, and hunting dogs. Among the guests were Geoffrey Chaucer, Petrarch, Jean Froissart and John Hawkwood. He the son of [her grandfather] King Edward III of England and [her grandmother] Philippa of Hainaut Queen Consort England.
On 7th October 1368 [her father] Lionel of Antwerp 1st Duke of Clarence died from poisoning at Alba. Duke Clarence extinct. Philippa Plantagenet Countess March 2nd Countess Ulster succeeded 2nd Countess of Ulster. He was buried at the St Pietro Ciel d'Oro Church, Pavia.
There was strong speculation he had been poisoned by his [her step-mother] wife's father.
On 24th August 1369 Edmund Mortimer 3rd Earl March, Earl of Ulster and Philippa Plantagenet Countess March 2nd Countess Ulster were married at Reading Abbey, Berkshire. She by marriage Countess March. He by marriage Earl of Ulster. She the daughter of Lionel of Antwerp 1st Duke of Clarence and Elizabeth Burgh Duchess of Clarence. He the son of Roger Mortimer 2nd Earl March and Philippa Montagu Countess March.
On 12th February 1371 [her daughter] Elizabeth Mortimer Baroness Camoys was born to [her husband] Edmund Mortimer 3rd Earl March, Earl of Ulster and Philippa Plantagenet Countess March 2nd Countess Ulster at Usk, Monmouthshire. She married 1. before 1393 Henry "Hotspur" Percy, son of Henry Percy 1st Earl of Northumberland and Margaret Neville, and had issue 2. after 21st July 1403 Thomas Camoys 1st Baron Camoys and had issue.
On 11th April 1374 [her son] Roger Mortimer 4th Earl March 3rd Earl of Ulster was born to [her husband] Edmund Mortimer 3rd Earl March, Earl of Ulster and Philippa Plantagenet Countess March 2nd Countess Ulster at Usk, Monmouthshire. He married 7th October 1388 Eleanor Holland Countess March and Ulster, daughter of Thomas Holland 2nd Earl Kent and Alice Fitzalan Countess Kent, and had issue.
On 21st November 1375 [her daughter] Philippa Mortimer Countess Pembroke, Arundel and Surrey was born to [her husband] Edmund Mortimer 3rd Earl March, Earl of Ulster and Philippa Plantagenet Countess March 2nd Countess Ulster. She married 1. 1388 John Hastings 3rd Earl Pembroke, son of John Hastings 2nd Earl Pembroke and Anne Manny Countess Pembroke 2. after 30th December 1389 Richard Fitzalan 9th Earl of Surrey 4th or 11th Earl of Arundel, son of Richard Fitzalan 3rd or 10th Earl of Arundel 8th Earl of Surrey and Eleanor Plantagenet Countess Arundel and Surrey 3. April 1398 Thomas Poynings 5th Baron St John of Basing, son of Luke Poynings 4th Baron St John of Basing and Isabel St John 4th Baroness St John of Basing.
Archaeologia Volume 22 Section XVI. What the Duke dyd after the Prince's death.
[After 8th June 1376] Prynce Edwarde beynge deade as we have sayed while the Parlement yett endured, the desperate knyghtes of the countyes began to be hautye & proud, & in the meane tyme the Duke with hys malefactours comynge in amongst the knyghtes with an oration earnestly desyred them, that yett whyle the Parlement endured wherein the matters of the realme were handled, the knyghtes, associated with the Lordes & Barons, wolde delyberate whoe after the deathe of the king & the prynce's sonne oughte to inherite the realme of Englande; furthermore he requested that after the example of France they wolde maike a law that no woman sholde be heire of the kyngdome, for he consydered the old age of the kynge, whom deathe expected in the gates, & the youthe of the prynce's sonne whom, (as yt was sayed) he purposed to poyson yf he colde no otherwayse come by the kyngedome; for if these tow were taiken away & such a law established in the generall parlement he was to be the next heire of the realme; for there was no heire maile in the realme nearer than he; but then yt was in every man's mouth, that [her husband] Edmunde Mortimer Earle of March had maryed the [her father] Lorde Lovellex hys brother's daughter [Philippa Plantagenet Countess March 2nd Countess Ulster], whoe was elder than he, to whom by righte of hys wyfe the inheritance of this realme perteined; yf the only sonne of the prynce sholde depart without an heire, whom the Duke greatly feared, knowynge hym to be a good & juste man, & therfor he laboured all that he colde, that the inheritance of this realme sholde not come to hym. Havynge begune therfor [to] consulte together, yt was answeared hym to be neadles to labour about such thynges, seying that they had other greate & weightier matters in there handes, that had neade to be largely handeled, & especially (sayed they) for that the kynge ys yett sounde & in healthe, & for hys age may lyve longer than any of us, but be yt granted the kynge sholde depart yet we want not an heire; the prynce's sonne (now ten years olde) lyves and is now lyvyng there ys no neade to labour about such matters. With these wordes the Duke confounded herewith departed.
On 10th December 1376 [her son] Edmund Mortimer was born to [her husband] Edmund Mortimer 3rd Earl March, Earl of Ulster and Philippa Plantagenet Countess March 2nd Countess Ulster at Ludlow Castle. He married 30th November 1402 Catrin Mathrafal, daughter of Owain Glyndŵr Prince Wales and Margaret Hamner, and had issue.
Around 1377 [her father] Lionel of Antwerp 1st Duke of Clarence was reburied at Clare Priory, Suffolk. Philippa Plantagenet Countess March 2nd Countess Ulster succeeded 5th Countess of Ulster.
In 1378 [her son] John Mortimer was born to [her husband] Edmund Mortimer 3rd Earl March, Earl of Ulster and Philippa Plantagenet Countess March 2nd Countess Ulster. There is some debate about his parentage. He married after 2nd January 1402 Eleanor Rossall.
On 27th December 1381 [her husband] Edmund Mortimer 3rd Earl March, Earl of Ulster died. He was buried at Wigmore Abbey. [her son] Roger Mortimer 4th Earl March 3rd Earl of Ulster succeeded 4th Earl March, 3rd Earl of Ulster, 6th Baron Mortimer of Wigmore.
On 5th January 1382 Philippa Plantagenet Countess March 2nd Countess Ulster died at Cork. She was buried at Wigmore, Herefordshire. [her son] Roger Mortimer 4th Earl March 3rd Earl of Ulster succeeded Heir to the Throne of England, 6th Earl of Ulster