As many facts as we have that John wrote the 4th gospel. It is issue of some debate with no acceptable proof as an answer. However, the larger number of scholars accept that he was a Gentile, writing to another Gentile. There is nothing in his writings to support the view that he was a Jew. In fact, his need to carefully investigate everything would appear to mean that he could not have written, as he did, without the major research that he did to produce both books. We read little, if anything, in his writings as we read in the other three gospels, although we know he, like Matthew, borrowed a lot from Mark and also a significant amount from 'Q'. He is included in the bible because he tells us about Yeshua's birth in some detail - without that we would only have Matthew, exceptionally brief account, and bridges the gap from gospel to Paul. Paul, who wrote before the gospels were written, tells us nothing about Yeshua's actual birth, surprisingly, even though he was't there; one might think he would 'justify' his works by including that matter!