I found quite a few relatives buried in Glasnevin during the nineteenth century, who share their plots with complete strangers. Some of those were infant children, buried remote from their parents, with complete strangers. There is something quite sad in that.
In another case, my great great grandfather lay alone in a grave for nearly a hundred years, until two brothers, complete strangers, were buried with him in recent years. I was very disappointed when I found the grave, to see a modern headstone to the two brothers, with no mention of my poor great great grandfather who lies forgotten beneath. I think I preferred where there was no gravestone at all. It's like my great great grandfather has no claim at all to his own grave!