Francis William Hart
born April 1873–April 1874
  in Blaisdon, Gloucestershire
died very roughly 1943
  in Gloucester

According to Leslie Hart: 'Frank [...] was a policeman—eventually Station Sergeant. It is known that he was posted for a time at Stow-on-the-Wold, also at Guiting Power in the Cotswolds. They had three daughters and one son—Gwen, Gertrude, Reginald and Rene.' Retired to, and died at, Armscroft Road, Gloucester.

Seems to be the relative remembered by Royston Hart:
Sergeant. Jolly man—big shock of grey hair. Had an Old English Sheepdog called Bunce. Lived at Armscroft Road, Gloucester. Had two daughters, one called Gwen.

A Francis William Hart was a witness to Thomas and Annie Maria's marriage—the same probably.

Not with parents in 1891 census.

1881 census: living in Blaisdon with parents, brothers, and lodger (William Ferris, 19, groom). Age is 7, and place of birth is Blaisdon.