How Manyskulls are there?

I know there's Victor Minsk, the one in the Nasrudin Tomb and I think two others in the Roseborough Cemetery. Plust the Siamese ones.

 

There are three in the Roseborough Cemetery, if you count Victor Minsk's father's skull. As for other skulls, the ones that you listed, plus the elder Minsk's skull, are the only ones that I recall finding, but I did find a reference to "The skull of Xin Ren'ar" in the Gamedescription.mes file, so there may be another skull that I have just never come across. This reference was just below the reference to the skulls of the Ren'ar Siamese twins, so it seems to be a different skull, but it could refer to one of the twins since I don't remember their names.