Akuma god

So I completed dies irae today and there is one thing I don't understand . . . . .. . . Who is the father of Lisa's twins in the world of Marie at the end of both rea routes where karl is not present ? Since Lisa 'did' Reinhard with the advice of mercurius and when they were going to make his body vessel which I think didn't happened in the marie world ( rea route ) right ? So I am really confused how rea and kasumi are the same as other routes they should be different no ? Or is Reinhard the father of the twins in Marie world ( rea route , after the new world is formed ) too ? Because Reinhard died in 1942 June 4 and Lisa gave birth to twins in 1942 as well so I don't understand . I hope it doesn't sound confusing . I am interested since they teased it for entire VN and they didn't went in proper detail about it so I would appreciate if someone tell me what happens in detail .