What we have is an edited, filtered version. The film indicates that Jesus had brothers and sisters and that Bethany is the distant niece of Jesus Christ. There is a complicated history behind this discussion. There is nothing in the early tradition to suggest that Jesus did not have brothers and sisters. It is only when the doctrine of Mary's perpetual virginity emerges that this passage, if read literally, becomes a problem.
Later interpreters deal with the problem by making different arguments.
Among these is the argument that Joseph had been married before and so Jesus' siblings were actually his stepbrothers and stepsisters. But there is no scriptural basis for this claim. The gospel of Mark does not mention the birth of Jesus at all, so we must assume that the writer of this gospel knew no tradition of an unusual birth. The gospels of Matthew and Luke handle the scandal of the unwed Mary's pregnancy in different ways. It is unclear from the texts themselves what meanings they attribute to Mary's virginity.