There's a few novels and (supposedly) non-fiction books based on the idea that Jesus had descendants, and at least one novel on a modern-day immaculately conceived daughter [1]. I'm not the right person to look at the theological implications of hereditable divinity (nor the genetic aspects) but the books provide some interesting lines of thought.Or if the twin lives and later has kids does Christianity eventually form similer to our timelines Islam with a eventual schism that factored into the sunni shia rift on weather or not to follow the word of the followers of Muhammad or his descendants going forward (in this the disciples and descendents)
The non-fiction books can vary - some are a bit 'My friend's brother's dentist told me about a page he'd seen in a copy of... in a private library. After five years of interesting sidetracks I finally tracked down the location only to find that the owner had moved/claimed the book didn't exist/ gladly showed me his library but the book or the page was missing/the house had been demolished and turned into a sports centre.'
Still quite fun if well written.
[1] Examples I've read.
Fiction - Da Vinci Code by Dan Brown, Only Begotten Daughter by James Morrow.
Non fiction - The Holy Blood and The Holy Grail, and The Templar Revelation.