Hello,
I think I can help...
I discovered James and Lillias Grant whilst researching my 2x Great Grandfather, John Grant (1818-1886). John's birth record says he was born at Mid Drum, Abernethy, the son of James and Lillias Grant. His death record shows his father as James Grant and his mother as Lillias Grant, maiden surname Grant (not Stuart).
On her 1868 death record, Lillias Grant is recorded as the widow of James Grant, farmer at Mid Drum and her parents are given as John Grant and Catherine Grant (Catherine's maiden name was also Grant).
James Grant was born on November 3, 1775 in Clachaig, Abernethy, Scotland. He died at Mid Drum, Abernethy on March 18 1863. On his death record his parents are named as Malcolm Grant and Janet MacPherson.
Great, Great Grandfather, John Grant was, I believe the eldest of six children so I am guessing James and Lillias married sometime around 1816/1817 although, that would put James in his 40's and Lillias in her 30's so I could be mistaken. John's siblings are Malcolm, Alexander, Lewis, James and Jannet.
'hope that helps separate the two families.