Their only son was a glass salesman and as far as I know never had any children. He was married in 1888 to Mina Louise Norman in New York, NY but I don't know what happened to his wife. She disappeared after the 1910 census in California.
William Gilbert Fulford died on May 5, 1919 in San Francisco, CA just a couple years after his parents. I suspect he was interested in family history himself since he joined the Sons of the American Revolution.
I located the record of his death several years ago but only recently found a funeral home record that was put online as part of the collection at the Mormon Church web page Family Search.
According to the Halsted Funeral Home record he died of a heart attack in route to Harbor Hospital and was buried at Cypress Lawn Cemetery, in what is now San Mateo County CA. I wanted to close the loop on this family and also find out if his wife was buried next to him so I asked a Findagrave volunteer to take a photo of the grave marker. Unfortunately they couldn't find it.
The cemetery can't find a record of his burial and they say he was cremated and returned to the funeral home. The funeral home said he was buried in the cemetery. At that time, if his wife had already died and he had no children or relatives in the area then being cremated would make sense. If she was still alive then I would think he would have been buried. Of course, maybe he just wanted his ashes scattered in the Ocean. He grew up around the water and his family for several generations made their living on it.