Joan had five sisters: Alianore became Countess of March ; Margaret became Countess of Somerset and later Duchess of Clarence; Eleanor became Countess of Salisbury; Elizabeth married Sir John Neville;[1] and Bridget became a nun at Barking Abbey.
Her eldest brother, Thomas Holland, 1st Duke of Surrey, was beheaded in 1400 by a mob of angry citizens at Cirencester for his role in the Epiphany Rising, which was aimed against the life of King Henry IV of England, who had usurped the throne of King Richard. Thomas's heir to the earldom of Kent was her second eldest brother Edmund Holland.
Edmund of Langley, 1st Duke of York (1341-1402) William Willoughby, 5th Baron Willoughby de Eresby (c1370-1409) Henry Scrope, 3rd Baron Scrope of Masham (c1373-1415) Henry Bromflete (c1375-1415)