What if Jogaila marries the daughter of Sigismund of Luxembourg, Elisabeth rather than marrying Sophia of Halshany and having their children marry each other to legitemize the Jagellonian dynasty, what will be the consequence of this marriage?
I'm affraid I don't understand. Jogaila should marry Elizabeth of Luxembourg - that I can follow (although since 1411 she was engaged to Albert II) but their children (i.e. children of Jogaila and Elizabeth) should marry each other? I'm pretty sure you do not propose an incest, so please, explain.
IIRC in Poland there was some talking about a marriage of Jogaila and Elizabeth of Luxembourg, only I think it was not about Sigismun'd daughter but Elizabeth of Goerlitz, duchess of Luxembourg (http://en.wikipedia.org/wiki/Elisabeth,_Duchess_of_Luxembourg). She refused.