Who is Mr. Ponza from Eleven Short Stories = Undici Novelle and what is their importance?

Mr. Ponza is the son-in-law of Mrs. Frola. Mr. Ponza claims his first wife, the daughter of Mrs. Frola, died and that he has remarried, but that Mrs. Frola refuses to believe that her daughter is actually dead. He says his second wife and he pretend she is Mrs. Frola's daughter to humor her in her delusion. He himself may be deluded, however, and the question is left open.