Sinclair research

This website is very much work in progress. It contains historical and genealogical details about the Sinclairs, in particular, the Anglo-Norman Saint Clairs in England, the Rosslyn and Herdmanston branches in Scotland, and the Irish branch that descended from the Rosslyn Sinclairs.

Every effort has been made to provide information based on historically verified documentation and updated with more recent academic research. However, histories of families in Ireland are notoriously difficult to research because of the loss of so many official records in Dublin in 1922, and church records only began in the 1700s. Sources of information for descendant tables of other Irish Sinclair families are largely based on online family trees and cannot be verified.

In Scotland the early history of the Sinclairs  was well documented by the Rosslyn family’s celebrated genealogist, Father Hay, and in The Enigmatic Sinclairs: The First 350 Years (2015) by Gerald Sinclair and Rondo B. B. Me, available from St. Clair Publications. Research is continuing and I would like to thank Nina Cawthorne for her new contributions to the study of the Scottish Sinclair families.

Information is presented geographically because the family’s unique history has been formed by past Sinclairs making periodic decisions to change their lives and circumstances: the Viking settlement of Normandy, the Norman invasion of England, establishing themselves in Scotland, planting in Ireland, and moving to England. Emigration to countries like America, Canada and Australia has also been the start of a significant new period of change.

Latest new and updated pages

Scotland, Rosslyn: St. Clair Earls of RosslynLords Sinclair of RosslynSinclairs of Sinklarsholm
Scotland, Herdmanston: St. Clair of HerdmanstonLords Herdmanston and SinclairSt. Clair of LongformacusSinclair of StevensonSinclair-Lockhart of Stevenson
Ireland: Sinclairs of Richhill


Medieval Walkern and Magna Carta, tracing the history of William and Hamo de Saint Clair from Normandy and William de Lanvalei from Brittany.

The Magna Carta Barons, describing the lives of the twenty-five barons whose army forced king John to agree to the 1215 Magna Carta.


A newsletter is published occasionally, providing details about new research. It can be subscribed or unsubscribed easily, and there is also an archive of password-protected past issues.


Many names are mentioned on this site, so the best way to find someone is to use the search box at the bottom of each page.