Their grave sites are easy to find. My great grandparents Thomas and Sarah Ann as well as my grandfather Russel, and my father Henry, are located very near to Robert Whitten's tomb which is a tall white marble monument featuring a column topped by an urn, and a darker coloured base. It is located right beside my family's graves, looking north away from the fence. You should see a gate behind you.
I don't know where my great great grandparents are buried.
To find these graves the best thing to do is enter the cemetery, and begin my walking west beside the fence that runs alongside Broadway.
I just took a look at the area using Google Maps and I can see their graves by using the zoom future.
Robert's brother's (Thomas) grave is further east and it is similar to Robert's monument except there is no column on top. It is a squat white marble monument with a darker coloured base.
I hope these instructions are helpful. If not, don't hesitate to contact me.