The claim that Jesus had siblings is problematic and, in fact, challenged within the camp of traditional Christianity.
The claim that anyone can trace their ancestry to Jesus is silly and unevidenced.
It is denied in the corpus of the faith that Jesus had any siblings at all. Some of the members of the corpus deny that Mary, married to Joseph ever had sexual congress with her husband at all.
I consider that to be non-evidentiary, under Hebrew law, Joseph would have been free to divorce her in that event. James, for one is mentioned in the Gospel as the brother of Jesus.
"6:2 And when the sabbath day was come, he began to teach in the synagogue: and many hearing him were astonished, saying, From whence hath this man these things? and what wisdom is this which is given unto him, that even such mighty works are wrought by his hands? 6:3 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? And they were offended at him.
6:4 But Jesus, said unto them, A prophet is not without honour, but in his own country, and among his own kin, and in his own house.
6:5 And he could there do no mighty work, save that he laid his hands upon a few sick folk, and healed them.
6:6 And he marvelled because of their unbelief. And he went round about the villages, teaching."
Regards,
Scott