Jane was the daughter of Edward Seymour, Duke of Somerset, and his wife, Anne Stanhope, the daughter of Sir Edward Stanhope and his wife, Elizabeth the daughter of Sir Foulke Bourghchier Lord Fitzwarin. Jane was the cousin of King Edward VI of England through her father's sister, Jane Seymour, who was the third wife of King Henry VIII.
Jane's father had previously been married to Katherine, the daughter and coheir of Sir William Fillot of Fillot, co Essex, Kt. and through this marriage, Jane was the half-sister of:
John Seymour, oldest son of the Duke of Somerset, who was buried on 19 December 1552 at the "hospetall of Savoy";
Lord Edward Seymour of Berry Pomeroy, co Devon;
Lady Jane Seymour died on 19 March 1560 (1561), aged 19, and was buried in the chapel of St Edmund, Westminster Abbey, where there is a mural monument to her, erected by Lord Hertford (her brother), with the inscription:
"The noble Lady Jane Seymour, daughter to the renowned prince Edward Duke of Somerset, Earl of Hertforde, Vicounte Beauchampe and Baron Seymour, and to the right noble Lady, Anne Duchess of Somerset his wyfe; departed this lyfe in her virginite at ye age of XIX yeares, the XIX daie of Marche A.D. M.CCCCC.LX, in the seconde yeare of the moste happie raigne of Queene Elizabeth, and was honorablie buryed in the floore of this chappel. To whose memorie, Edward Earle of Hertforde and Baron Beauchampe, her deare brother, hathe caused this monument to be made"
at after-none at Westmynster [was
brought] from the quen('s) armere a my lade Jane Semer, with [all the quire] of the abbay, with ijC. of (the) quen('s) cowrt, the wyche she was [one] of the quen('s) mayd(s) and in grett faver, and a iiijxx morners of [men and] women, of lordes and lades, and gentylmen and gentyllwomen, all in blake, besyd odur b of the quen('s) preve chambur, and she [had] a grett baner of armes bornne, and master Clarenshux was the harold, and master Skameler the nuw byshope of Peterborow dyd pryche. [She was] bered in the sam chapell wher my lade of SufFoke was.