I don't, hence the question of the G_d gene. If G_d manifested as a wholly human being, then Jesus was just that wasn't He? IE a wholly human being. If G_d manifested and still had godly attributes (doesn't that then diminish the story slightly - as if Jesus was still G_d, then how easy to ignore temptation and pain as G_d is all powerful), then do those 'descendants' also have godly powers? Is that what Shasta or the 'Magdalene and Jesus had kids' followers believe? I never quite understood what Christianity believed (and I don't think Christians themselves had any hard and fast 'concept' - wasn't that part of Nicaea?) and I don't think the 'Jesus had descendants' followers have come to a conclusion about what that actually means. Are the descendants 'of the same substance as G_d' (wasn't that the belief enforced by Nicaea?), human...a mixture...?
According to the Nicene Creed Jesus is God who became man:
We believe in one Lord, Jesus Christ, the only Son of God, eternally begotten of the Father, God from God, Light from Light, true God from true God, begotten, not made, of one Being with the Father. Through him all things were made. For us and for our salvation he came down from heaven: by the power of the Holy Spirit he became incarnate from the Virgin Mary, and was made man.
The key points being 'of one Being with the Father', meaning He was supposedly the same 'entity' as God, and 'was made man'. This means Jesus, according to the above at least, was both God and man at the same time. He was supposedly a man who could be bashed up and confused, and He ate and crapped etc. However, as an omnipotent God He could also supposedly make a couple of fish into a pile of fish, walk on water and raise dead people back to life. As a man who ate and crapped, it would seem reasonable to assume that He could also ejectulate. As an omnipotent God, it would seem reasonable to assume that He could impregnate anyone or anything He wanted, woman or banana. He had, after all, only a few decades earlier impregnated His own mother by way of carrier-pigeon.
It just seems to me that whichever way you look at it, the descendants aren't that special. Either they are human and have no specific godly powers. Or they are G_d and the hundreds/thousands/millions of them that may exist today are what - also all G_d? - but they haven't done anything with whatever power they have - so what difference the power?
The only relevance that these hypothetical people would have would be the relevance people gave them. But never underestimate just how credulous some people really are!