time travel paradox

[carlruby]

A friend and i were discussing the new terminator movie to be released. In the first movie a man sends a friend back in time to save his mother, the friend then gets his mother pregnant with him, so his friend becomes his father.
Leaving aside whether time travel could be one day possible, could sucha senario exist?

[joeblow90]

Since his friend is not in any other way related to him, there would be no reason why not, there is no paradox as his friend would always have been his father. There was an oldish tv movie called "the flipside of dominic hyde" and a sequel in which dominic via time travel becomes his own grandfather. This wouldnt be possible as his Y chromosome (among others) would have no origin.