Did Jesus have siblings??  

I saw that programme and although it was fairly interesting, I'm not sure that much was actually found out about Jesus's family. I, personally, believe that Jesus did have more family than just Mary and Joseph. Even if the theory that Joseph was a widower with children from his first marriage were true, that would still make those children Jesus's family, although not blood related assuming Jesus was actually the son of God and not human. Also, even if you believe that Mary was a perpetual virgin, her and Joseph no doubt had brothers and sisters of their own so Jesus would have had uncles, aunts, cousins, etc. so whichever way you look at it, Jesus MUST have had other family. And if those siblings were all older than Jesus then yes they could have been from a previous marriage of Joseph but, as I said before, they are still Jesus's family.

Matt 13:55 Is this not the carpenter's son? is not his mother called Mary? and his brethern, James, and Joses, and Simon, and Judas?
Mark 3:31 There came then his brethern and his mother, and, standing without, sent unto him, calling him.
There are more verses than this, but I think you get the picture. Yes Jesus had brothers, and possibly sisters.

This is not at all hidden - it is in the New Testament that the Lord Jesus Christ had brothers and sisters.

Matthew 13:55-56 state: "Is this not the Son of the carpenter? Is not the mother of Him being called Mariam and the brothers of Him Iakobos and Ioseph and Simon and Ioudas? And the sisters of Him are they not all with us? Therefore from where did all these things come to this?"

Other verses related to this are Matthew 12:47; Mark 3:22; 6:3; Luke 8:19-20; John 2:12; 7:3, 5, 10).

Joseph the husband of Mary was not a widower. Matthew 1:25 states:

"and he was not knowing her until which time she delivered the Son; and he called the name of Him Iesous."

Joseph and Mary were husband and wife and were authorized to copulate, there is no prohibition. Take note "until which time she delivered the Son" which means that Joseph and Mary had no sexual relationships until the birth of Jesus. Afterwards, they were not prohibited and so they had other sons and daughters after the birth of Jesus.