Who says Jesus has a sister?

The Bible does. Two of the Gospels are quite clear on that point.

The Gospel of Matthew, Chapter 13, verses 55 & 56:

Is not this the Carpenter's son? Is not his mother called Mary? And his brethren, James and Joses and Simon and Judas?

And his sisters, are they not all with us?

The Gospel of Mark, Chapter 6 verse 3:

Is not this the carpenter? The son of Mary, the brother of James and Joses and of Juda and Simon? And are not his sisters here with us?

When I first read these I thought that it was possible that by 'sister' they could mean 'cousin' as the ancient peoples often referred to more distant relations as being 'brethren' and, with the intermingling of families, cousins could be regarded as brothers and sisters. However, I've been assured by several scholars of Koine (Biblical Greek), and by my own Greek Lexicon, that the words used (ai adelphai) are not those used for cousins but for blood-brothers and sisters. The word used for cousin is 'sougenos'—as used for Elisabeth, cousin of Mary.

I was discovering this at exactly the same time as I read an article in The Times which said that the Pope had declared once and for all that Jesus did not have any brothers or sisters. Such is life!

In fact, Deborah's story seemed to stem naturally from her being born to a different mother from Miriam (Mary) to explain why she had such a different religious outlook from that in orthodox Nazareth. Deborah hates the Jewish God having learnt nothing to help her to see any good in religion. When she and her sister, Salome, move to Nazareth they are faced with a great deal that is new.

In Roman society at that time children were often adopted from one part of a family to another and it is entirely likely, given the short life-expectancy of both men and women in those days, that it happened in all societies. Boys in particular were adopted if one branch of the family had several sons and other had no son. A cousin's boy would be raised as the son of the household instead.

Roman women only lived an average of 27 years! (Source: The Roman Mother, by Suzanne Dixon, published by Croom Helm). If they managed to survive the dangerous years of childbearing then they would generally outlive the men as still happens now.

Many years later, when I wrote The Marriage of Jesus, I took the idea further examining the idea that if Jesus started his ministry at approximately the age of 30 and women often died young, it was quite possible that he was a widower when he came to John the Baptist to be baptised. I'm not really a fan of the 'he married Mary Magdalene' theory as it's a) historically unlikely as the Gospels make it clear she was a woman of independent means and if she were Jesus' wife her means, legally, would have been his and b) I think it's a bit of an insult to say she could only have been spiritually important because of an intimate relaitonship with Jesus...But you'll have to read the book for the background details of that.

Incidentally, should you be interested in finding out more about Yeshua/Jesus' relations you could look at Jack Kilmon's web-site. Jack is a scholar who is fascinated by the lineage of Yeshua ben Miriam.