On 28 Jun 1648 [his father] Henry Seymour (age 22) and [his mother] Mary Capell Duchess Beaufort (age 17) were married at Little Hadham, Hertfordshire [Map]. He the son of William Seymour 2nd Duke Somerset (age 60) and Frances Devereux Duchess of Somerset (age 48). They were fourth cousins. He a great x 4 grandson of King Henry VII of England and Ireland.
In 1654 William Seymour 3rd Duke Somerset was born to Henry Seymour (age 28) and Mary Capell Duchess Beaufort (age 23).
On 30 Mar 1654 [his father] Henry Seymour (age 28) died. He was buried at Bedwyn Magna Great Bedwyn, Wiltshire.
On 24 Oct 1660 [his grandfather] William Seymour 2nd Duke Somerset (age 72) died. His grandson William Seymour 3rd Duke Somerset (age 6) succeeded 3rd Duke Somerset, 2nd Marquess Hertford, 3rd Earl Hertford.
Before 25 Dec 1660 [his step-father] Henry Somerset 1st Duke Beaufort (age 31) and [his mother] Mary Capell Duchess Beaufort (age 30) were married. He the son of Edward Somerset 2nd Marquess Worcester (age 58) and Elizabeth Dormer.
Pepy's Diary. 30 May 1667. Several fine experiments were shown her of colours, loadstones, microscopes, and of liquors among others, of one that did, while she was there, turn a piece of roasted mutton into pure blood, which was very rare. Here was Mrs. Moore of Cambridge, whom I had not seen before, and I was glad to see her; as also a very pretty black boy that run up and down the room, somebody's child in Arundel House [Map]. After they had shown her many experiments, and she cried still she was full of admiration, she departed, being led out and in by several Lords that were there; among others Lord George Barkeley (age 39) and Earl of Carlisle (age 38), and a very pretty young man, the Duke of Somerset (age 13).
On 12 Dec 1671 William Seymour 3rd Duke Somerset (age 17) died. His uncle [his uncle] John Seymour 4th Duke Somerset 1645-1675 (age 26) succeeded 4th Duke Somerset, 3rd Marquess Hertford, 4th Earl Hertford. Sarah Alston Duchess Somerset 1642-1692 (age 29) by marriage Duchess Somerset.
Paternal Family Tree: Seymour
Maternal Family Tree: Elizabeth May Viscountess Campden 1562-1643
Kings Wessex: Great x 19 Grand Son of King Edmund "Ironside" I of England
Kings Gwynedd: Great x 16 Grand Son of Owain "Great" King Gwynedd 1100-1170
Kings Seisyllwg: Great x 21 Grand Son of Hywel "Dda aka Good" King Seisyllwg King Deheubarth
Kings Powys: Great x 16 Grand Son of Maredudd ap Bleddyn King Powys 1047-1132
Kings England: Great x 5 Grand Son of King Henry VII of England and Ireland
Kings Scotland: Great x 14 Grand Son of William "Lion" I King Scotland
Kings Franks: Great x 15 Grand Son of Louis VII King Franks
Kings France: Great x 8 Grand Son of Charles "Beloved Mad" VI King France
Great x 4 Grandfather: John Seymour 9 x Great Grand Son of King John "Lackland" of England
Great x 3 Grandfather: Edward Seymour 1st Duke Somerset 6 x Great Grand Son of King Edward III of England
Great x 4 Grandmother: Margery Wentworth 5 x Great Grand Daughter of King Edward III of England
Great x 2 Grandfather: Edward Seymour 1st Earl Hertford 5 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: Edward Stanhope
Great x 3 Grandmother: Anne Stanhope Duchess Somerset 4 x Great Grand Daughter of King Edward III of England
Great x 4 Grandmother: Elizabeth Bourchier 3 x Great Grand Daughter of King Edward III of England
Great x 1 Grandfather: Edward Seymour 2 x Great Grand Son of King Henry VII of England and Ireland
Great x 4 Grandfather: Thomas Grey 2nd Marquess Dorset 4 x Great Grand Son of King Edward III of England
Great x 3 Grandfather: Henry Grey 1st Duke of Suffolk 5 x Great Grand Son of King Edward III of England
Great x 4 Grandmother: Margaret Wotton Marchioness Dorset
Great x 2 Grandmother: Catherine Grey Countess Hertford Great Grand Daughter of King Henry VII of England and Ireland
Great x 4 Grandfather: Charles Brandon 1st Duke of Suffolk 6 x Great Grand Son of King Edward "Longshanks" I of England
Great x 3 Grandmother: Frances Brandon Duchess of Suffolk Grand Daughter of King Henry VII of England and Ireland
Great x 4 Grandmother: Mary Tudor Queen Consort France Daughter of King Henry VII of England and Ireland
GrandFather: William Seymour 2nd Duke Somerset 3 x Great Grand Son of King Henry VII of England and Ireland
Great x 1 Grandmother: Honora Rogers
Father: Henry Seymour 4 x Great Grand Son of King Henry VII of England and Ireland
Great x 4 Grandfather: Walter Devereux 1st Viscount Hereford 4 x Great Grand Son of King Edward III of England
Great x 3 Grandfather: Richard Devereux 5 x Great Grand Son of King Edward III of England
Great x 4 Grandmother: Mary Grey Baroness Ferrers Chartley 4 x Great Grand Daughter of King Edward III of England
Great x 2 Grandfather: Walter Devereux 1st Earl Essex 6 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: George Hastings 1st Earl Huntingdon 4 x Great Grand Son of King Edward III of England
Great x 3 Grandmother: Dorothy Hastings 5 x Great Grand Daughter of King Edward III of England
Great x 4 Grandmother: Anne Stafford Countess Huntingdon 4 x Great Grand Daughter of King Edward III of England
Great x 1 Grandfather: Robert Devereux 2nd Earl Essex 7 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: Robert Knollys
Great x 3 Grandfather: Francis Knollys
Great x 4 Grandmother: Lettice Peniston
Great x 2 Grandmother: Lettice Knollys Countess Essex 6 x Great Grand Daughter of King Edward III of England
Great x 4 Grandfather: William Carey 4 x Great Grand Son of King Edward III of England
Great x 3 Grandmother: Catherine Carey 5 x Great Grand Daughter of King Edward III of England
Great x 4 Grandmother: Mary Boleyn 7 x Great Grand Daughter of King Edward "Longshanks" I of England
GrandMother: Frances Devereux Duchess of Somerset 8 x Great Grand Daughter of King Edward III of England
Great x 4 Grandfather: James Walsingham
Great x 3 Grandfather: William Walsingham
Great x 4 Grandmother: Eleanor Writtle
Great x 2 Grandfather: Francis Walsingham 8 x Great Grand Son of King Edward "Longshanks" I of England
Great x 4 Grandfather: Edmund Denny
Great x 3 Grandmother: Joyce Denny 7 x Great Grand Daughter of King Edward "Longshanks" I of England
Great x 4 Grandmother: Mary Troutbeck 6 x Great Grand Daughter of King Edward "Longshanks" I of England
Great x 1 Grandmother: Frances Walsingham Countess Essex 9 x Great Grand Daughter of King Edward "Longshanks" I of England
Great x 4 Grandfather: Richard St Barbe
Great x 3 Grandfather: Henry St Barbe of Ashington Somerset
Great x 2 Grandmother: Ursula St Barbe
William Seymour 3rd Duke Somerset 1654-1671 5 x Great Grand Son of King Henry VII of England and Ireland
Great x 4 Grandfather: Edward Capell 10 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 3 Grandfather: Henry Capell 11 x Great Grand Son of King Henry "Curtmantle" II of England
Great x 2 Grandfather: Arthur Capell 6 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: Thomas Manners 1st Earl of Rutland 4 x Great Grand Son of King Edward III of England
Great x 3 Grandmother: Catherine Manners 5 x Great Grand Daughter of King Edward III of England
Great x 4 Grandmother: Eleanor Paston Countess Rutland
Great x 1 Grandfather: Henry Capell 7 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: Thomas Grey 2nd Marquess Dorset 4 x Great Grand Son of King Edward III of England
Great x 3 Grandfather: John Grey 5 x Great Grand Son of King Edward III of England
Great x 4 Grandmother: Margaret Wotton Marchioness Dorset
Great x 2 Grandmother: Margaret Grey 6 x Great Grand Daughter of King Edward III of England
Great x 4 Grandfather: Anthony Browne 4 x Great Grand Son of King Edward III of England
Great x 3 Grandmother: Mary Browne 5 x Great Grand Daughter of King Edward III of England
Great x 4 Grandmother: Alice Gage
GrandFather: Arthur Capell 1st Baron Capell Hadham 8 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: Thomas Montagu 6 x Great Grand Son of King Edward "Longshanks" I of England
Great x 3 Grandfather: Edward Montagu 7 x Great Grand Son of King Edward "Longshanks" I of England
Great x 2 Grandfather: Edward Montagu 8 x Great Grand Son of King Edward "Longshanks" I of England
Great x 4 Grandfather: John Roper of Well Hall
Great x 3 Grandmother: Helen Roper
Great x 1 Grandmother: Theodosia Montagu 9 x Great Grand Daughter of King Edward "Longshanks" I of England
Great x 4 Grandfather: John Alexander Harrington
Great x 3 Grandfather: James Harrington
Great x 4 Grandmother: Elizabeth Moton
Great x 2 Grandmother: Elizabeth Harrington
Great x 4 Grandfather: William Sidney
Great x 3 Grandmother: Lucy Sidney
Great x 4 Grandmother: Anne Pakenham
Mother: Mary Capell Duchess Beaufort 9 x Great Grand Daughter of King Edward III of England
Great x 2 Grandfather: Charles Morrison 6 x Great Grand Son of King Edward III of England
Great x 4 Grandfather: John Hussey 1st Baron Hussey of Sleaford 9 x Great Grand Son of King John "Lackland" of England
Great x 3 Grandmother: Bridget Hussey Countess Bedford 5 x Great Grand Daughter of King Edward III of England
Great x 4 Grandmother: Anne Grey Baroness Hussey Sleaford 4 x Great Grand Daughter of King Edward III of England
Great x 1 Grandfather: Charles Morrison 7 x Great Grand Son of King Edward III of England
Great x 3 Grandfather: Nicholas Clerke
Great x 2 Grandmother: Dorothea Clerke
GrandMother: Elizabeth Morrison Baroness Capell Hadham 8 x Great Grand Daughter of King Edward III of England
Great x 4 Grandfather: John Hicks
Great x 3 Grandfather: Robert Hicks
Great x 2 Grandfather: Baptist Hicks 1st Viscount Campden
Great x 1 Grandmother: Mary Hicks Lady Cooper
Great x 3 Grandfather: Richard May
Great x 2 Grandmother: Elizabeth May Viscountess Campden