Catherine Stewart

Brad Verity wrote:[1]

She is called second daughter of the 1st wife in DP and CP sub Forbes (1926), 1st daughter of the 2nd wife by BEP, and listed as the 2nd daughter in SP Atholl (1904).

No marriage contract or settlement survives to verify the first name and marriage of this daughter of Atholl. We do have this, from a genealogy of the Forbes family written by one Matthew Lumsden, around the year 1580, when he died:

"Next to him succeeded John Lord Forbes, the third brother, gray Willie's youngest son, who married Dame Katharine Stewart, daughter to Earle John of Atholl, who bear to him James Master of Forbes, who died unmarried, whilk was a great pitie and dolor to them yt. knew him; and a daughter called Elspet, who was married on the Laird of Grant, and his Ladie departed but further succession: and after her death, the sd. Lord John married Dame Christian Lundie, daughter to Sr John Lundie of that ilk"

https://archive.org/stream/genealogyoffamil00lums#page/10/mode/2up

As Matthew Lumsden, the author of the above, was married to an illegitimate daughter of John, 6th Lord Forbes, presumably he was familiar enough with the family to correctly report the first name and parentage of the 6th Lord's Stewart wife. 

Katherine Stewart died before 26 February 1510, when King James IV approved Forbes's settlement on his second wife Christine Lundy:

https://archive.org/stream/registrummagnisi02scot#page/734/mode/2up

Katherine Stewart's surviving child Elizabeth Forbes married James Grant, 3rd Laird of Freuchie, and three of their children were married in 1539, 1545, and 1553, pointing to births for them in the 1520s. Chronology then suggests that Elizabeth Forbes was born around 1500, and that in turn her mother Katherine Stewart fits better as a daughter of the 1st Earl of Atholl and his second wife.

This is only guesswork. The 6th Lord Forbes doesn't have an entry in ODNB and only has a barebones account in CP, making it difficult to determine any links with the Stewarts of Atholl that could help to date his first marriage.

Sources

• http://archiver.rootsweb.ancestry.com/th/read/GEN-MEDIEVAL/2014-05/...
• Source: Sir James Balfour Paul, The Scots Peerage: founded on Wood's Edition of Sir Robert Douglas's Peerage of Scotland. (Edinburgh: David Douglas, 1908-1919. 9 vols.), IV:54. (No entry in Vol. 9, corrections)
• Source: G E C et al, Complete Peerage (St Catharine press, London, 1910 on), V: 545 (Forbes). (No entry in Vol XIV, corrections)

Katherine Stewart Born about 1473 in Of, Aberdeenshire, Scotland Daughter of John Stewart and Margaret (Douglas) Stewart Sister of Jean (Stewart) Arbuthnot [half], Elizabeth (Stewart) Gray, Joanna (Stewart) Gordon, Christian Stewart [half], Elspeth (Stewart) Innes [half], Isabel (Stewart) Robertson [half], Elizabeth (Stewart) Ross [half], John Stewart [half], Elizabeth (Stewart) Robertson [half], Jean Stewart [half], Andrew Stewart [half], Margaret Stewart [half] and Mariote (Stewart) Campbell [half] Wife of John Forbes — married before 1508 in Scotland Mother of Elizabeth (Forbes) Grant and James Forbes Died about 1515 in Scotland

1463 Traquair, Peebleshire, Scotland Death: February 26, 1510 (47) Scotland Immediate Family:

Daughter of Sir John Stewart, 1st Earl of Atholl and Lady Margaret Douglas, Countess of Douglas Wife of John Forbes, 6th Lord Forbes Mother of James Forbes and Hon. Elizabeth Forbes Sister of Isabella Stewart; Jean Stewart, Countess of Huntly; Elizabeth Stewart and Anne Stewart Half sister of Marjory Stewart; Margaret Stewart; Elspeth Stewart; John Stewart, 2nd Earl of Atholl; Christian Stewart; Lady Elizabeth Stewart; Jean Stewart; Andrew Stewart, Bishop of Caithness; Jean Stewart; Elizabeth Stewart; Henry Stewart; Malcolm Leslie, First Laird of Cults and Andrew Leslie of Pitscurry

Katherine Stewart Born about 1473 in Of, Aberdeenshire, Scotland Daughter of John Stewart and Margaret (Douglas) Stewart Sister of Jean (Stewart) Arbuthnot [half], Elizabeth (Stewart) Gray, Joanna (Stewart) Gordon, Christian Stewart [half], Elspeth (Stewart) Innes [half], Isabel (Stewart) Robertson [half], Elizabeth (Stewart) Ross [half], John Stewart [half], Elizabeth (Stewart) Robertson [half], Jean Stewart [half], Andrew Stewart [half], Margaret Stewart [half] and Mariote (Stewart) Campbell [half] Wife of John Forbes — married before 1508 in Scotland Mother of Elizabeth (Forbes) Grant and James Forbes Died about 1515 in Scotland