Are there any known descendants of the family (brothers and sisters) of Jesus Christ alive today?

Given that nobody is even certain whether Jesus Christ had any siblings, it would be very difficult to establish any descendants. The Bible contains references to brothers and sisters, and provides names for some of them, but the problem is that the actual word used in the original text does not necessarily imply the kinship relationship that we would understand when it is translated as brother/sister.

Three principal views have been advanced:

(1) that they were Jesus' actual siblings/brothers, that is, half brothers, sons of Joseph and Mary (and therefore younger than Jesus);

(2) that they were His stepbrothers, that is, children of Joseph by a previous marriage (and thus all older than He and not His blood relatives at all);

(3) that they were the cousins of Jesus on the mother's side, according to some, or on Joseph's side, according to others.

http://www.bibleinfo.com/en/questions/did-jesus-have-any-brothers-andor-sisters

There are various theories Jesus has a bloodline existing today, mainly based on the possibility he was married to Mary Magdalene. https://en.wikipedia.org/wiki/Jesus_bloodline