Jesus was not Jewish.
Jesus never converted to Judaism. He originated from Galilee, a fully Hellenized city by the Ptolemies (Greeks) and later the Seleucids (Greeks), with a large proportion of its residents consisting of Greek colonists, and Greek as the official language, without this implying that he was Greek or embraced the religion of the Greeks and Hellenists of region. Jews themselves called him ironically "Nazaret" (from Nazareth, province of Galilee). He denies that he is son of David (that has Jewish ancestry, that is), does not accept the God of Abraham and the Jewish faith Yahweh calling him a "dead God", as he also denies to be the "king of the Jews" when Pilate asked him. He was tried in Roman court and not in the Jewish one, and did not keep the Sabbath.