Oh, I was thinking, what if upgrading the cave and getting underground caverns allowed Krobus to move in without using up the wife slot? The dwarf could also move in if you befriended him too and you saw the event in which Krobus and the dwarf are forced by the wizard to make peace.
Korbus's room could be at the southeast corner of the Farm caverns in an area that looks like old sewers cut from the rest of the sewage system, and the second farm minecart would be neart that spot. While the dwarf could get a room on the north side of the caverns near the stairs leading down from the farm cave, all the way on the other side of the caverns, because they would still give each other a wide berth.