There is quite a few. Basically different Pokemon might appear in the same horde when either they are counterparts or when they are based off similar things.
So for counterparts you might see (these are ones I have actually seen) Tauros & Miltank or Plusle & Minun. I'm guessing (but haven't actually seen Illumise & Volbeat or Solrock & Lunatone are other ones, although this list is obviously not exhaustive.
For same design you get things like Sudowoodo and Trevenant (i think that was in a trailer at some point) among others.