Family/Spouse: Unknown. [Group Sheet] [Family Chart]

1. John (Sir) (of Herdmanston & Polworth) St Clair and died.
2. William (of Herdmanston & Polworth) St Clair and died.

John + Elizabeth Polwarth. Elizabeth and died. [Group Sheet] [Family Chart]

Notes:

Herdmanston in East Lothian had been held from the 12th century, when Henry St Clair received a grant of the lands of Herdmanston, from Richard de Morville, Constable of Scotland. It is not known if the Sinclair Lords Herdmanston share a common origin with the Sinclair Barons of Roslin from whom also branch off the Lords Sinclair and Earls of Caithness.

According to the website sinclairgenealogy.info, the fact that that the first proven Baron of Roslin, William St. Clair (died 1297) was made sheriff of Haddington in East Lothian where Herdmanston also is, suggests that he was appointed there to cover his own home area, and given that the name William appears frequently in the St Clair of Herdmanston family suggests that he may have been part of their extended family.

However, according to the website clansinclairusa.org, William St Clair of Roslin was probably unrelated to the St Clairs of Herdmanston.

The Sinclairs of Herdmanston are recorded by James Balfour Paul in his The Scots Peerage.[5] They are also recorded by Bernard Burke in his a Genealogical and Heraldic Dictionary of the Peerage and Baronetage of the British Empire.

Their hereditary coats of arms are recorded by 18th century herald, Alexander Nisbet in his A System of Heraldry.

The coat of arms of the Sinclair of Herdmanston family is similar to that of the Lord Sinclair, but the tincture of the azure cross was changed to sable.

(Research):Lords Herdmanston
Roland Saint-Clair writing in the late 19th century lists the following Lords Herdmanston:[2]

Henry Sinclair, 1st Lord Herdmanston
Alan de Sinclair, 2nd Lord Herdmanston (fl. c. 1244)
John Sinclair, 3rd Lord Herdmanston (fl. c. 1248)
John de Sinclair, 4th Lord Herdmanston (fl. c. 1296) Said to have been killed 25 Aug 1330, Teba de Ardales, Spain
William Sinclair, 5th Lord Herdmanston (fl. c. 1325) Also said to have been killed 25 Aug 1330, Teba de Ardales, Spain
William Sinclair, 6th Lord Herdmanston (fl. c. 1364)
John Sinclair, 7th Lord Herdmanston (fl. c. 1381)
William Sinclair, 8th Lord Herdmanston (fl. c. 1407)
John Sinclair, 11th Lord Herdmanston (fl. c. 1434)
John Sinclair, fiar of Herdmanston (fl. c. 1472)
William Sinclair, 12th Lord Herdmanston (fl. c. 1451)
John Sinclair, 13th Lord Herdmanston (fl. c. 1481)
William Sinclair, 14th Lord Herdmanston (fl. c. 1513)
John de Sinclair, 15th Lord Herdmanston (fl. c. 1545)
William Sinclair, 16th Lord Herdmanston (fl. c. 1586)
John Sinclair, 17th Lord Herdmanston
Henry Sinclair, 18th Lord Herdmanston
William Sinclair, 19th Lord Herdmanston
John Sinclair, 20th Lord Herdmanston
John Sinclair, 21st Lord Herdmanston
John Sinclair, 22nd Lord Herdmanston
John Sinclair, 23rd Lord Herdmanston, married Catherine Sinclair, daughter and heir of John Sinclair, 10th Lord Sinclair
Henry Sinclair, 24th Lord Herdmanston and 11th Lord Sinclair
John Sinclair, 25th Lord Herdmanston (died 1750)
James Sinclair, 26th Lord Herdmanston
Charles Sinclair, 27th Lord Herdmanston (died 1775)
Andrew Sinclair, 28th Lord Herdmanston
Charles Sinclair, 29th Lord Herdmanston (fl. c. 1782)