Megan & Son

With reading about Henri von Leuschner, it turns out that Demetri played by Peter Porte is his nephew, the question that I have is with what I read was that he was played by G’vera in flashbacks & the character had died in the 80’s, was this before Megan was presumed to be dead & did Henri have siblings, if he never did explain as to how Dimitri is his nephew, I can’t see Megan being impregnated by her own brother, don’t you think? She did bring up, I forgot when she brought up that she did marry Dimitri’s father, so explain did Henri have siblings & if so, then howcome it can’t be found anywhere of Henri having siblings?