According to Scotland's People James Marshall and Elizabeth Hamilton had seven children in the parish of Shotts, Lanarkshire:
Elizabeth, 1794
Margaret, 1796
Agnes, 1796
James, 1799
John, 1802
Thomas, 1804
Richard, 1812
Are these the James Marshall and Betsy Hamilton you are looking for?
I see from the SP index to the census that Francis Whitecross was in Dundee in 1841 aged 20, in Dundee in 1851 aged 30 and in Perth in 1861 aged 40, but not after that. There does not seem to be a death certificate. Do you know what happened to him?
In 1851 there are in Dundee Francis Whitecross, 30; Helen, 34; James, 12; Willm, 8; David, 5; and Hellen, 3. In 1861 there are in Perth Francis, 40; Ann, 28; Willm, 17. Have you looked at the originals of these censuses?
However SP has no baptisms of children to Francis Whitecross and Helen Marshall.
In 1881 Helen Whitecross, widow, aged 76, born Armagh, Ireland is in Liff and Benvie with her daughter Margaret, 38, born Dundee. If that age is correct she would have been born in 1804/1805, not 1816/1817 as suggested by her age in the 1851 census. (And where was Margaret in 1851, when she would have been just 8 years old?)
In 1861 Hellen Whitecross, 44, was in Dundee with David, 15 and Hellen, 14, but I can't find her in 1871.
Helen Marshall or Whitecross died in Dundee in 1882, aged 65. Have you seen her death certificate? Is that where you got her parents' names from?
I note from SP that a Francis Whitecross married Ann Laird in Dundee in 1883. Did Francis leave his wife and set up house with Ann Laird, whom he married as soon as was decorous after his wife's death? Or was this a different Francis Whitecross?
So far, there seems to be no evidence to link the Marshalls with Kirriemuir or any where else in Angus. Why do you think the Marshalls (as opposed to the Whitecrosses) may have had anything to do with Kirriemuir?