Thanks for clearing up genpin.
There are a couple more: MM1_keyboard, moepro, ftaerobi, mpsaikyo, moepro90, terao, mptennis, moepro88, smoepro.
I'd prefer if they were not in the listxml output if they don't really exist as game sets.

When looking at the -listxml output, there are a couple of roms that claim to be derived from a parent that is not included in the -listxml output. The most glaring one is "genpin" but there are about a dozen more. I think this is a bug. Either the parent should be included in the -listxml...