He does not pay rent, but has he contributed to the home in any way? Has he paid any utilities, bought food or furniture, or contributed for at least a time in some small part? As implied by Gail, what form of verbal contract was made to dad? How long has he resided in the home?

Does he have his own room? And is that room open to the owner or other residents?

Are BOTH owners on board with the eviction? If he is the guest of one of the owners, an eviction is unlikely.

If both owners/sisters are seeking the eviction then he can likely be evicted without much difficulty ... provided he doesn't contest it (which may only serve to delay the inevitable).

And, as a "lodger" he has much the same rights as a "tenant" (Civil Code 1940(a)).