"fake ossuary that attempted to promote the idea that Jesus Christ had brothers casting doubt on the virgin birth of Christ."
Sounds like this crook was more interesting stealing money more than making a religious statement.
That said, presuming that James was the younger (half)brother, there would be no doubt "cast" on the issue of the virgin birth.
If memory serves, Jesus also had 2 younger sisters- Miriam and Martha- in addition to his younger brother James, who, as I recall was the Bishop of the Jerusalem Church in the years following the Crucifixion.