Old school Scienty Fiction:

[MaryL]

All you zombies. Rob Heinlein: A Sex changing time traveler pro created with him/herself and created multi level paradoxes from 1959. In other words: I am my own grandpa.

 

[Bob Blaylock]

All you zombies. Rob Heinlein: A Sex changing time traveler pro created with him/herself and created multi level paradoxes from 1959. In other words: I am my own grandpa.

Made into a movie, some years back, titled Predestination.

The original short story can be found here.