The man's father is my father's son

The question:
"Brothers and sisters I have none. That man's father is my father's son"
 who is the man? and who is "I"?


logical reasoning:
  "I" have no brother and sister, so I am the only child of my father, therefore, my father's son should be "I", the speaker.
 Then the man's father should be I.
So the man is the speaker's son, and I is the speaker.