If this is the one I think it is, there are in fact 13 unrelated people buried there over 1925-26. Only the soldier has a headstone, which looks as if it is quite recent. I'll PM Sandra with the list.
Many cemeteries, including Epsom, have "private" and "public" graves. With private graves, exclusive burial rights are purchased, usually for a family, and for a set period of time like 75 years or even in perpetuity, though the latter is uncommon nowadays. The owners usually have a right to erect a monument such as headstone and/or kerbs.
With public (aka "common") graves, there are no such rights and unrelated people are buried together. One of my relatives is with 18 strangers, and I've known 30 or more. Headstones may or may not be permitted and where they are and relatives can afford them, they tend to be miniature ones less than knee height. You'll often see rows of them one behind the other like dominos. I've also seen full size headstones with multiple unrelated names. Public graves are obviously cheaper and often referred to as "pauper's graves", though I think this term should really be applied to those buried "on the parish".
Burial of a child in the private grave of friends or strangers who died around the same time was a common practice until quite recently and may still happen. The kind explanation was "so the child wouldn't be lonely", but harsher reality was that unless you could afford it, no one wanted to bother opening a grave for a baby.
If you look up a relative somewhere like Deceasedonline and it says "buried with X others" and X is half a dozen or more, then it was either a private grave of a large, rich family or a public one and you may have difficulty finding it. With the present shortage of burial space in towns, public grave areas of cemeteries are now the first to be reused for ashes plots or new burials by piling several feet of earth on top, and your relative's grave will be unrecognisable.
