Please tell us ALL the details you have at the start rather than later mentioning bits that make a difference to the searches we do trying to help you.
Since you probably don't know the Philadelphia area-
In 1920 Bill & Norah Gemmill & son were living at 321 North Narberth Ave., Lower Merrion, Montgomery Co. (slightly northwest of Philly)
https://familysearch.org/ark:/61903/1:1:MFYV-PKKHonor B. Gemmell who died 1980 is buried in West Laurel Hill Cemetery, Bala Cynwyd, Montgomery Co.
Both places are in Lower Merrion Township and only about 2 miles apart. Collingwood, N.J. is only about 15 miles from the cemetery.
Not all records are on Find A Grave so I suggest you contact the cemetery to ask what details they have for Honor B. Gemmell and anyone else buried in the same plot. Also ask if Robert C. Gemmell/Gemmil's there.