Hi Aislin,
It baffles me too but I believe the family are innocent on this occasion as, sadly, I think the father James, who died in 1933, was the last of the immediate family since David seems to have been their only child. James died in Paisley; his death was registered by his brother-in-law and he must have been taken back up to Forfar to be buried with his wife so I don't think there would be many tending the grave. I do feel sorry for him to have lost his wife in 1914 and his only son two years later - I had been hoping to find siblings of David but drew a complete blank so am working on earlier generations.
Transcription of the headstone:
Erected by
JAMES THOM
IN LOVING MEMORY OF
HIS WIFE
ANN McINROY TASKER
WHO DIED 10th MAY 1914
AGED 56 YEARS
ALSO THEIR SON
Pte DAVID LOW THOM
H.C. BATT ROYAL
WARWICKSHIRE REGIMENT
KILLED IN FRANCE
19th JULY 1916, AGED 21 YEARS
THE ABOVE
JAMES THOM
WHO DIED 29th MARCH 1933
AGED 75 YEARS
THOM
The only thing I'm not 100% sure of is whether Regiment is in full or abbreviated to REGT.
Regards
Michelle