Frederick Charles Ford (my great grandfather)

1861 born, on September 9th
spent early years at Causeway Farm, Radipole
1863 baptised at St Ann's on April 5th
1883 married Mary Jane Hann on December 4th
1891 census, living in Weymouth Road, Radipole next to Field Barn Cottage
1914 stated occupation as farmer on Percy's marriage certificate, put his name as Charles Ford. At this time he may have been farming close to Radipole at Coldharbour, Chickerell
1933 occupation: farmer, living in a thatched cottage in Radipole
1951 died

his children
Harold Charles (married Emily), died 1972
Mabel Constance
Mildred Jane (witnessed Percy's wedding in 1914)
Percy George - my Grandfather
Ethel Ruby born early 1886 and died October 1886. Buried in St Ann's.
Frederick Charles Ford in 1915
Frederick Charles Ford (centre) in 1915, stood behind his wife Mary and his daughter-in-law Fanny.
On his right is his son Harold, and Harold's wife Emily. Their son Charles is sat on the chair in front of them.
On Frederick's left is his son Percy (my grandfather) and a daughter who must be Ethel (labelled as Ruth on the photo).

Another possible interpretation of this photo is that the elderly woman seated in front of my great grandfather is his mother, not his wife. Esther Ford (nee Bartlett) died at Causeway Farm, Radipole in January 1912. If this photo was taken in 1911, not 1915, she would have been 80 years old. In which case why is my great grandmother not in this photo?