According to Epiphanius (church father/saint), the Ebionites (an ancient Jewish sect) believed that Paul was not Jewish. Infact Jews today will also tell you the same thing. Just ask the center for Jewish studies "Paul was born pagan and converted to Judaism; or he belonged to Hellenistic Judaism which was regarded as an inauthentic kind of Judaism; he believed that the messiah had come and that the Law could be transcended in the new messianic age, his background had been in Jewish mysticism.