It may be worth your ringing the relevant Rhondda Cynon Taf Council on the following numbers (listed below):
Quoted from Rhondda Cynon Taff Website
http://www.rhondda-cynon-taff.gov.uk"If you have any queries concerning burial or any other cemetery matters please contact your local cemetery on the numbers below.
Telephone:
Taf Cemeteries
01443 402810
Rhondda Cemeteries
01443 772336
Cynon Cemeteries
01685 885345/885346"
I am not 100% sure which one is the one to ring but I would bet on the Rhondda Telephone number. They may be in a position to give you more information on a grave number etc before any search is made of the graveyard.
There is also a publication (CD) by the Glamorgan Family History Society available on this cemetery named "Trealaw Cemetery Burial Records 1881- 1990". This CD is an index of people buried at Trealaw Cemetery, Rhondda. The cemetery is also known as Llethyrddu. It is an index of the burial registers and not monumental inscriptions.
The burials are indexed by surname followed by the first name/s, plot number and year of burial. It can be searched on any of the fields and multiple burials in the same grave can be found by searching on the plot number.
The original internment notices are deposited at Treorchy library where they can be consulted and photocopies made. The library will photocopy them for those who are unable to travel to Treorchy, but they do charge a small sum for this service. More information can be found here:
http://www.rootsweb.com/~wlsglfhs/I hope this helps
Regards Jen