I have only just started researching my mothers side of the family and I came across your posting.
My grandmother was Martha Yuill Low (b.13 September 1908 in Kircaldy, Fife in Scotland; d.1986 Johannesburg, South Africa). She married my Granddad Alfred William Steer in South Africa on 22 April 1930. She had a twin sister Margaret Low, another sister Catherine Low and a brother James Low who all lived in a small town called Belfast in South Africa.
Her mother was Martha Yuill Armour (b.14 April 1884 in Calderhead, Lanark, Scotland; d. 22 April 1962 Transvaal, South Africa). She was married to James Low (b.1881 Scotland; d.1961 Transvaal, South Africa). Sorry, I don't have an accurate date on his birth and death to the day.
Martha Yuill Armour's mother was Martha Yuill who was married to John Armour (b.1845; d. 16 February 1902). They were married on the 31st December 1868 in Lanark, Scotland).
John Armour's parents were James Armour and Jean Donald. I have it that they were married at Avondale, Lanark, Scotland on 6 March 1841.
I hope this helps. If you have progressed any further with your research on this line, I would love to have that. If you need any more info on my Grandmothers line in South Africa, please let me know.