Today something really stupid happened to me. To show the new iPhone I gave it to a friend at work. He activated Siri and said:

"Call my father"

Siri said : "Who is your father?"

My friend said his name and since he was in the address book contacts the phone called his number. Now every time I say "Call my father" my friends number is called. How can I delete this "relationship" and where is it stored?