Question about dies irae ( spoilers )

[Akuma god]

So I completed dies irae today and there is one thing I don't understand .

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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 . 

[ArgentstR]

Did you read Omnia vincit Amor? It seems to be Trifa in that ending, I'm guessing it's safe to assume it's the same in Rea's route.