Dingbatt: I have to ask, is all this personal information you are volunteering being stored on Apple's Siri Server to maximise its assistance to you?
No. Siri creates an addition to the owner of the iPhone's contact book that says "Sister" and has the name of the person's sister. ect. ect.
But ...nevertheless....big brother is watching you! ***insert evil laugh*** wuuuuhahahahaha!