On May 19, 1359 Blanche of Lancaster married John of Gaunt, her third cousin at Reading Abbey. Blanche was the second daughter of Henry of Grosmont, Earl of Lancaster and joint heiress to her father's estates along with her elder sister, Maud. The death of Henry occurred in 1361 followed shortly by the death of Maud in 1362. The result of which was that Blanche and John inherited a large number of estates and titles including that of the Duchy of Lancaster. Together they had several children half of which died in infancy. In 1367 Blanche gave birth to a boy Henry who was to become king of England as Henry IV. In 1369 John of Gaunt went to France to fight for Edward III, but on his return in November he found that Blanche had died in the September. Although John of Gaunt married twice more, he chose to be buried in St. Paul's Cathedral alongside Blanche. The tomb showing the couple holding hands.

 Blanche (of Lancaster) (b.1342? - d.1369)
    +John (of Gaunt, Duke of Lancaster) (b.1340 - d.1399)
        = Henry (IV, King of England 1399-1413) (b.1367 - d.1413)
        |   +Bohun, Mary (b.1368? - d.1394)
        |   |   = Henry (V, King of England 1413-1422) (b.1387 - d.1422)
        |   |   |   +Catherine (of Valois) (b.1401 - d.1437)
        |   |   |       = Henry (VI, King of England 1422-1461, 1470-1471) (b.1421 - d.1471)
        |   |   = Thomas (Duke of Clarence) (b.1389 - d.1421)
        |   |   |   +Holland, Margaret (b.1385 - d.1439)
        |   |   = John (of Lancaster, Duke of Bedford) (b.1389 - d.1435)
        |   |   |   +Jacquetta (of Luxembourg) (b.1415? - d.1472)
        |   |   = Humphrey (Duke of Gloucester) (b.1390 - d.1447)
        |   +Joanna (of Navarre) ( - d.1437)
        = Philippa, (daughter of John of Gaunt)
        |   +John (I, of Portugal)
        = Elizabeth (daughter of John of Gaunt)
            +John (Earl of Pembroke - 1389)