Is it possible to be related to Pocahontas through her son Peregrine Smith that she had with John Smith?

Yes, it is possible. There are varying accounts historically of what happened with and between John Smith (Smyth) and Pocahontas. It depends on who's "version" of history you believe. There is evidence of Peregrin Smith born in Jamestown in 1608 at which time Pocahontas would have been 13 or 14 - certainly of child bearing age. There is too much evidence otherwise to dismiss these historical traditions. The only way to verify a connection would be to have DNA testing on a Rolfe family descendant and yourself to see if there is a match that would connect Pocahontas.