The
Wikipedia article on the Talpiot tomb has a summary of the arguments.
The main argument that the original Talpiot tomb is the "Jesus family" is (as
crich70 remembers) based on probabilities calculated for the appearance of the names, which correspond to Jesus son of Joseph, Mara (taken to be Mary, mother of Jesus), Yose (taken to be Joses, Jesus's brother), Jude son of Jesus, and Mariamne (taken to be Mary Magdalene, who is further identified as Jesus's wife).
One of the criticisms with this interpretation of the evidence is that they're trying to use the presence of "Mariamne" both as evidence that Jesus was married to Mary Magdalene
and as evidence that this is likely the tomb of the "Jesus Family". One can't properly do both, but that's where
The Lost Gospel comes in. Barrie Wilson believes that "The Confession of Asenath" (which can be read in a translation from 1900
at Google Books) is, instead of a Jewish romance as it appears at first glance, actually a gnostic Christian parable that can be interpreted to mean that Jesus was married to Mary Magdalene.
Jacobovici then claims to have
external evidence that Jesus and Mary Magdalene were married to justify his earlier probabilities.
Where James Tabor fits into this is that he thinks that Jesus's brothers James, Jude and Simeon were the same people as the
disciples James, Judas and Simon Peter. He believes that James took leadership of the Jerusalem church after Jesus's death and he sees existence of a Jesus family tomb in Jerusalem as supporting evidence for this.