Note on his father's findagrave.com site indicates they may have had a daughter, Myra, wife of Vernon Fox; and Estella.
"Died at Italy Hill, Thursday, Oct. 19th, 1882, Gavin E. Doubleday, in the 57th year of his age. Mr. Doubleday was the eldest and last surviving son of the late Hon. Elisha Doubleday of Italy Hill. He died at the home upon which he settled in early life. His disease, dropsy, was of a painful and lingering nature, and he passed away welcoming his release, as an entrance to desired rest. His loss is keenly felt by friends and surviving relatives." (Yates County Chronicle 16 November 1882)
Gavin's wife, Ammira Gload, was the sister of his brother Evert's wife, Sarah.