General Notes

Who William's parents were is controversial
"See also Robert de Saintclair & Eleanor de Dreux in this file)

E mail from Jim Weber
"Burke's Peerage (under Caithness) also indicates that William Sinclair's parents are Robert de Saint Clair, in Normandy and Eleanor de Dreux. Burke's also indicates that William married Amicia dau of Henry de Roskelyn and received the Barony of Rosslyn via charter from Alexander II from Henry de Roskelyn."


However after much research Doug Hickling writes:
"I mentioned what THE SCOTS PEERAGE had to say about the early Sinclairs.  It says in relevant part:

William (Sir) Sinclair, according to Father Hay, was the son of Robert de Saintclair   in Normandy, and his wife Eleanor, relict of Hugh, Lord of Chateauneuf, daughter  to Robert, second Comte de Dreux, in France  by Joland of Coucy, his wife.

THE SCOTS PEERAGE account says nothing of any connection with Blanche of Navarre or Eleanor of Aquitaine.  Father Richard Augustin Hay lived in the household of the Sinclairs of Rosslyn in the 17th century or so.  Interestingly, a copy of his GENEALOGIE OF THE SAINTECLAIRES OF ROSSLYN, published in 1835 with notes by an unidentified editor who points out that Hay's work is sometimes flawed, does not show the lines as cited by THE SCOTS PEERAGE.  In fact, this version of Hay's genealogy of the Sinclairs, at 2-3, shows the descent of the Sinclairs to be from "one William (Sir) Sinclare, second sone to Woldonius or Wildernus, in France, whose mother ws daughter to Duke Richard"--an uncle of William the Conqueror.  No mention is made of the de Dreux family or of Blanche of Navarre.  It is, of course, possible that the editor chose to correct what he regarded as Hay's mistakes, but, because the text is in 17th century English, it appears that the editor did not touch Hay's text.    

I have looked at everything I can find on the Sinclairs and none of these accounts give any creedance to the connection with Eleanor of Aquitaine. 
Indeed, these books do not even show a Robert St Clair in the line of  descent except for one account, SAINT-CLAIRS OF THE ISLES, by Roland William Saint-Claire, published in 1898, which, at page 277, shows the same information, apparently from the same source that was relied upon several years later in THE SCOTS PEERAGE, but with a dotted line from Robert de Saintclair to William (Sir) De St Clair, indicating a possible, but doubtful, father-son connection.  The same chart shows the De Dreux connection but does not suggest any descent from Blanche of Navarre or Eleanor of Aquitaine.

All of the other sources show that William (Sir) was descended from Mauger or Malger, an uncle of William the Conqueror.  Thus, the highly respected HISTORY OF THE SINCLAIR FAMILY IN EUROPE AND AMERICA, by Leonard Allison Morrison, published in 1896 and which is currently available in a reprint, refers to Walderne Sinclair as the "father of William Sinclair, founder of the Sinclairs of Scotland, and shows his line of descent as "Malger 5, Richard 4, William Longsword 3, Rollo 2, Rogenwald 1."

The Sinclair family has a very elaborate website at www.clansinclairusa.org, that has a great many articles and genealogical histories of the Sinclairs. 
Detailed family lineage charts are entitled THE NORSE YEARS, THE NORMANDY YEARS, THE CRUSADER YEARS, THE NORMANDY YEARS, AND THE TEMPLAR YEARS, after which the line divides.  The  line shown on the Clan Sinclair website starts with Fornjot b. c. 610.

I will pick up the line starting with Rognvald:

1.  Rognvald, 1st Earl of Orkney born c. 830.  Married Ragnhilda, daughter of Sea King Rolf Nefia.

2.  Hrolf (Rollo) 860-933, 1st Duke of Normandy.  Married Poppa, daughter of Count Berenger of Bayeaux.

3.  Duke William, Longsword, 2nd Duke of Normandy, born c. 870 - died c. 942, murdered by Arnulf of Flanders.

4.  Duke Richard I, the Fearless, 3rd Duke of Normandy, born c. 925 - died 20 November 996.  Married Emma, sister of King Hugh Capet of France.  Emma's mother was the daughter of the King of England.  Married Gunnor (Albereda), daughter of Danish settlers.

5.  Mauger, Count of Mortain & Corbuel, born c. 986 - died 1040.  Do not
confuse this Mauger with his nephew Mauger, the son of Duke Richard II (our Mauger's brother), who was the 6th Archbishop of Rouen.

6.  Walderne, Lord of St Clair, born c. 1004 - d. 1047.  Married Helene, a natural daughter of Duke Richard II.

7.  William, The Seemly, 1st Baron of Rosslyn, born 1028 - died 1070. 
Married Dorothy Agnes Dunbar.  William accompanied the family of Edward the Atheling from Hungary to England 1057.  Fought then for Malcolm III with the English rebels who supported Edgar the Atheling for King of England.  He was with Margaret's group as she fled England on the way back to a Hungarian nunnery.  He was later killed by troops of his cousin William the Conqueror on the Scottish borders in Northumberland.  Given Rosslyn by Malcolm for life rent.

8.  Henry (Sir) Sinclair, 2nd Baron of Rosslyn, born 1060 - died c. 1110. 
Married Rosabel Forteith, daughter of Earl of Strathern.  Given Rosslyn
forever.

9.  Henry (Sir) Sinclair, 3rd Baron of Rosslyn, born c. 1100 - died c. 1180.  Married Margaret Grathenay.

10.  William Sinclair, 4th Baron of Rosslyn, born c.1130 - died 1214. 
Married Agnes Dunbar, daughter of Earl Patrick March.

11.  Henry Sinclair, not a baron as the baronship passes over him to his son Henry.  Born c. 1160.  Married Katherine, daughter of the Earl of Strathern.

12.  Henry Sinclair, 5th Baron of Rosslyn, born c. 1190 - died 1270.  Married Margaret, daughter of the Earl of Mar.

13.  William Sinclair, 6th Baron of Rosslyn, born c. 1240 - died 1297 at the Tower of London.  Married (2) Matilda, daughter of Magnus V of Orkney (Nisbet).  Their daughter Annabel married David (Sir) Wemyss.

14.  Henry, 7th Baron of Rosslyn, born c. 1275 - died 1336.  Married Alice de Fenton.  Led Knights Templar to victory at Bannockburn. 

15.  William Sinclair, born c. 1300 - died 25 August 1330 with his brother John at Teba, Spain, while fighting the Moors while with James (Sir) Douglas carrying King Bruce's heart to the Holy Land.  Married Rosabelle.  He died before his father so he did not become Baron.

16.  William, 8th Baron of Rosslyn, born c. 1327 died c. 1359 in Lithuania with the Teutonic Knights.  Married Isabella, daughter of Malise II, 20th Earl of Orkney.

17.  Prince Henry, 9th Baron of Rosslyn, 1st Sinclair Earl of Orkney, born c. 1345 - died c. 1402.  Married (2) Janet Haliburton, daughter of Thomas (Sir) Halyburton, Lord of Dirleton Castle.  On June 2, 1398, he arrived with 12 boatloads of Templars at Chadebucto Bay, Nova Scotia.  Went on to Massachusetts and Rhode Island.

NOTE:  I am doubtful of the website's listing of Thomas (Sir) Halyburton
instead of Walter (Sir) Halyburton of Dirleton as the father of Henry's wife. 
THE SCOTS PEERAGE, volume 6, at 569, says that it was Walter (Sir).  I will look into it.

18.  Henry, 10th Baron of Rosslyn, 2nd Sinclair Earl of Orkney, born 1369 - died 1420.  Married Egidia Douglas, daughter of William Douglas of Nithsdale and Princess Egidia Stewart.

Of course, the website materials continue on through the Sinclair Earls of Caithness, etc.  As much as I would like to confirm the Sinclair connection with Eleanor of Aquitaine, I am sure that all of the Sinclair researchers would have the same intereSt  If none of these researchers has been able to make the connection, I would tend to think that there is no support for it other than hope.

As you know, there is no recent history of the Sinclair family.  From looking at the ClanSinclairusa website, it appears that the recently deceased Clan genealogist, H. S. Cummings, wrote and published through Higginson Books of Salem MA two books.  One is entitled THE GENEALOGY OF PRINCE HENRY SINCLAIR, and is supposed to cover 26 generations."

See also Stirnet Genealogy at
'Sinclair01'
http://www.stirnet.com/HTML/genie/british/ss4as/sinclair01.htm#drumm
Families covered: Sinclair of Caithness, Sinclair of Dun, Sinclair of Mey, Sinclair of Murchil, Sinclair of Orkney, Sinclair of Ratter, Sinclair of Roslin

Main sources: TSP (Orkney), BE1883 (Orkney), TSP (Caithness), BP1934 (Caithness), TSP (Sinclair), BP1934 (Sinclair).

TSP = "The Scots Peerage", founded on Wood's Edition of Sir Robert Douglas's "Peerage of Scotland". Edited by Sir James Balfour Paul. Published 1908.

BE1883  = Burke's Extinct Peerage "Genealogical History of the Dormant, Abeyant, Forfeited and Extinct Peerages of the British Empire by Burke" (1883 edition).
Copies of this are held in many of the larger public libraries in the UK."

BP1934  = Burke's Peerage and Baronetage "A Genealogical and Heraldic History of the Peerage and Baronetage" by Sir Bernard Burke, 92nd edition. Published by Burke's Peerage Ltd in 1934.

Shows his parents as                
Robert de St Clair (in Normandy)
m. Eleanor de Dreux (dau of Robert II, Count of Dreux)
1. Sir William Sinclair of Roslin (a 1264, Sheriff of Edinburgh)
  m. Amicia