You write that the son did not pay rent: that makes him a guest, not a tenant. If the parent was the sole owner and the daughter has the legal authorit to act in his behalf, then she can remove him: a property owner can remove a guest, even a family member guest, at will, and someone who is the custodian or guardian of an incompetent legal guardian can therefore remove the guest, too, since she has the same authority as the property owner. If he will not leave when asked to leave, a legal action can be brought to remove him, though if he's not a tenant, the proper action to bring is an "action for ejectment," not an eviction proceeding (eviction is for tenants; ejectment is for non-tenants). It is likely that a court would, however, exercise its equitable authority in  case like this to delay the ejectment of a disabled man so as to give him or his guardian time to find an alternative living situation, so don't expect a quick resolution to this case. Because ejectment is a more complex action than tenant eviction, and there is the added element that the son is disabled, the daughter is advised to retain an attorney to help her.If the son's mother is part owner of the condo, however, then he can't be removed in this way: she has the right to let him stay in property which she owns. Then the only option is to bring a legal action seeking a court order forcing the sale of the property and the division or distribution of the proceeds, which order would include him being removed. Expect this could take quite some time.