The sons of Zebedee are named, not twice, my bad, but at the end.
The internal evidence that gives clues to the beloved disciple ( if you do not read into it that he may be John Son of Zebedee):
He is called the beloved disciple.
Only one other is ever mentioned as being the one the Jesus loves: Lazarus.
The majority of the GOJ happens around Jerusalem, where Lazarus lives.
There are accounts that only a member not typically associated with Jesus as one of the 12, could have access to, like being by Jesus at the cross.
Jesus leaves his mother in the care of the beloved disciple, which would mean that he had means and a home to care for her, which we know Lazarus had.
The final chapter seems to set apart the the beloved disciple from the ones actually named.
In short, there is enough "gray areas" to accept that it may not be John, son of Zebedee.
There is also the writing, that is more inline with an educated Jew than a fisherman.
Which, according to:
Smith's Bible Dictionary
(whom God helps), another form of the Hebrew name Eleazar.
Lazarus of Bethany, the brother of Martha and Mary. (John 11:1) All that we know of him is derived from the Gospel of St. John, and that records little more than the facts of his death and resurrection. The language of (John 11:1) implies that the sisters were the better known. Lazarus is "of Bethany, of the village of Mary and her sister Martha." From this and from the order of the three names in (John 11:5) we may reasonably infer that Lazarus was the youngest of the family. All the circumstances of John 11 and 12 point to wealth and social position above the average.
Seems to add some weight to the view.