As ar as there being a grave, if he lived in Tylorstown /Maerdy or Ferndale, then he could be buried in Ferndale or Llanownno cemetery. I don't think Penrhys cemetery was opened unitl the 1920's. It is possible if he lived nearer Wattstown or Ynyshir, that he might be buried at Trealaw. If you have the birth certiicate of the last child, then the address may give a clue as to the most likely cemetery. There is for example John Jones buried at Ferndale IN 1907 Plot C58 (D). Internment 4714.
https://www.findagrave.com/memorial/146255405/john-jonesUnfortunately there are no other details recorded, so diicult to know if this John is even an adult.
However, if you contacted Treorchy or Pontypridd library, they could look up his internment record and email you a copy. This would give details of name, address, occupation and other relations possibly.
Given the short span of years in which the death is likely to have occurred, the librarian would I'm sure be able to search and find all relevant John Jones's during that time, at all relevant cemeteries in the Rhondda for which they hold records (including possibly relevant local chapels).
Do you have any details of John's marriage to Lily Alice ?