I’m sorry, ImNotMad2, but there are serious problems with the traditions that we inherited. I think that it is too much to claim that the named authors cannot be the people that tradition names, but there are serious difficulties with most of the traditional claims.
John Mark, may have been a companion of Peter, but then why do the references prior to Papias always associate him with Paul, and not Peter?
The claim that Matthew the Apostle was also Matthew the Evangelist is extremely weak (and its source, Papias, is notably unreliable). If the actual statement of Papias is true, then the collection of sayings that Papias mentions is clearly not the same as the Gospel that we now have, which was written forty years or so later with a clear dependence on Mark. Why would an eyewitness base so much testimony on the writings of someone who was, at best, one generation removed?
Peter, the fisherman, is almost certainly not the author of the two letters in his name, both of which are written in literary Greek and one of which was copied from the letter of Jude.
Neither the letter of James nor the letter of Jude make any personal references to Jesus as a person, creating the odd situation in which someone who was supposed to have been a brother appeals not to the preachings of Jesus but to the authority of the Church when proclaiming their message.
(Appeals to Luke and Mark as the companions of Peter and Paul, if true, do not make them eyewitnesses to Jesus.)
Again, I do not claim that any named person cannot be the actual author, but most of the testimony of authorship dates to the period sixty years after the letters were supposed to have been written and even those reports are second hand. (E.g., we only have the quotations from Irenaeus (mid 2d century) and Eusebius (4th century) regarding what Papias might have written–we have no works by Papias, himself.)