Marriage for Mary Mein 16 May 1830 Dumfries to James Stewart
1851 census Glen Harvey New Abbey transcribed as Stwart on Ancestry
James Stewart age 46
Mary Stewart age 44 born Troqueer
Alex 18,John 16, Margaret 13 ,James 10 Jane 7
Still there on the 1861 census
The wording on the grave stone is a bit jumbled knowing who is the son or daughter of who

But I would say the Alexander that died 1870 is the son of Mary and James and Margaret that died in Liverpool 1902 also their daughter ..Probate record for her she never married
Rosie