Do i have to move my cats if my dad is having a liver transplant?

I think so: I do recall cats having the potential to cause infectious disease problems with transplant patients. Check with the transplant coordinator or surgeon to be sure.

Litter box far away: We worry about the infection toxoplasmosis with cats. This is transmitted by "oocysts" in their stool. So, please keep your cats indoors (to decrease risk of new infection picked up outdoors), keep them away from food surfaces, and wash hands carefully before food preparation. Your dad should not clean the litter box. This info is supported by the cdc (centers for disease control + prevention).