They should be fine. I keep kribs with South American cichlids all the time. Put a few flowerpots in the tank for the kribs and they'll mind their own business. Sometimes spawning kribs are feisty, but that goes for most any cichlid.
Kribs should be fine. Theyre pretty placid, as are severums, though I wouldnt put juvi kribs with large severums. A small cave or two, or flower pot, or something the krib can fit in by himself is all thats needed.