In the Third Word from the Cross (John 19: 26), Jesus commends his mother to the disciple John. From my study on this text for my midweek sermon last night, I discovered again that there is a dispute as to the exact nature of Jesus' family. I brought this up in a previous post regarding the perpetual virginity of Mary, as claimed by some. Admittedly it is curious why Jesus' mother and her sister and John are by the cross, and the rest of Jesus' family is missing. True, if those so mentioned in the gospels were his brothers, they did not yet believe in Jesus as the Messiah (John 7:5). This is one reason used to explain why Jesus chose John to care for his mother instead of the so-called siblings.
It is clear that Joseph is now deceased by this point. He is omitted from discussion from the very beginning of Jesus' ministry. Jesus is the eldest, and it is responsibility to care for Mary. Committing her to John's care would be one reasonable argument to explain that those called "brothers" are missing. Using the alternate translation they were simply "cousins" or other relatives who did not have the responsibility to care for Mary as a son would.
The question of Jesus' siblings, for me, is an "open question." I think that the witness in the gospels allows for it, but I can understand the argument against it as well. I realize that Luther is said to have held to the perpetual virginity of Mary. However, that being said, I don't think that this elevates it to a point of doctrine.
Back to that previous post I mentioned a moment ago, a reader noted that it had to do with the doctrine of Christology (if I am recalling correctly.) Yet, how would believing that he had brothers and a sister take away from his status as the "only Son" of the Father? How would it diminish his divinity? Perhaps I am missing something here. Is there a reference in the Confessions that illuminates this point? Or, is it, as I noted before, simply an "open question"?