Born into a prominent gentry family, he is best known as the father of Henry VIII's third wife, Jane Seymour, and hence grandfather of king Edward VI of England.

Jane Seymour, the eldest surviving daughter, was a maid of honour to Henry's first wife, Catherine of Aragon, and later to Anne Boleyn.

[37][38] The monument gives his age at death as sixty: "This Knight departed this Lyfe at LX years of age, the XXI day of December, Anno 1536 and was firste buryed at Eston Priorie Churche amongst divers of his auncestors, bothe Seymours and Sturmyes..."[2][3] His eldest son and heir, Edward Seymour, inherited lands producing an income of £275 a year,[9] equivalent to £203,362 in 2023.

His monument in Great Bedwyn church consists of a chest tomb displaying heraldic escutcheons, surmounted by his recumbent effigy, fully dressed in armour with hands in prayer, his head resting on his helm from which projects the sculpted Seymour crest of a pair of wings.

[39] On the wall above is a tablet inscribed as follows:[40] "Here lyeth intombed the worthie Sr John Seymour of Wolfhall, Knight, who by Margerie his wyfe, daughter of Sr Henry Wentworthe, Knight, from whome the nowe Lorde Wentworthe is discended, had sixe sonnes and fower daughters, to wete, John who dyed unmaryed; Edwarde, Duke of Somerset, Earl of Hertforde, Vicount Beauchampe and Baron Seymour, uncle to Kinge Edwarde the Sixt, Governor of his Royall Person, Protector of all his Dominions and Subjects, Lorde Treasorer and Earle Marshall of Englande; w[i]ch Duke maryed Anne, daughter of Sr Edwarde Stanhope, Knight, by Elizabeth his wyfe, daughter of Sr Foulke Burgchier, Lorde Filzwaryn [sic], from whome the moderne Earles of Bathe are discended; Sr Henry Seymour, Knight, who maried Barbara daughter of Thomas Morgan, Esquier; Thomas Lorde Seymour of Sudeley, Highe Admirall of Englande, who maryed Katherine, Queene of Englande, and wydow to Kinge Henry the Eight.

Jane Qveene of Englande, wyfe to Kynge Henry the Eight, and mother to Kynge Edwarde the Sixt; Elizabeth, firste maryed to Sr Henry Ughtred [sic], Knight, after to Gregorie, Lorde Cromwell, and last to Jhon Lorde Sainct John of Basinge [sic], after Marquesse of Winchester; Margery, who dyed in her infancy, and Dorothe, maryed to Sr Clement Smythe, Knight.

This Knight departed this lyfe at LX yeares of age, the XXI day of December, Anno 1536, and was firste buryed at Eston Priorie Churche amongst divers of his auncestors, bothe Seymours and Sturmyes.

Howbeit that Churche beinge ruyned, and thereby all theire monumentes either whollie spoyled, or verie much defased duringe the mynoritie of Edwarde, Earle of Hertforde, sonne to the said Duke, the said Earle after, as well for the dutyfull love he beareth to his said grandefather, as for the better contynuans of his memory, did cause his bodie to be removed, and here to be intombed at his own coste and chardge, the laste daye of September, Anno 1590, in the XXXII yeare of the moste happye raigne of our gratious Soveraigne Ladie Queene Elizabeth."