Yours does not sound like this is the case, but for example I have a few family members who have three or four, several died in war. Their burial is at the place of death burial site (overseas), the family put a Cenotaph stone in the local family cemetery plot, another side of the family put a Cenotaph marker is yet another cemetery, then the US moved the the battlefield burials to the closest National cemetery. So now there are four grave stones for same person, all over the world. This is just one example.
In reading into yours though, sounds like several people have created graves on cemetery sites for same person, based off their belief the person is there. I have worked a few of those out also, mine turned out that family on two sides, both claimed different cemeteries. And the people creating the cemetery sites memorials found cemetery or newspaper records which claimed the two different cemeteries. For me I really do not know which cemetery is correct and most likely never will.