User blog comment:Abyssal Horror/Mind blowing theory/@comment-4851119-20130717141553/@comment-4851119-20130718140738

They don't have to exist in the same universe for Sigmar to be a Lost Primarch... Warp affects Fantasy too, or they wouldn't have Chaos with their own versions of the Ruinous Gods, which BTW they do. Primarch II or XI could've come out of the Warp in the Fantasy-verse still an embryo, conveniently inside Sigmar's mother's uterus, and then been born and raised as Sigmar. his Gestation Pod was seperated, and fell from the sky as that twin-tailed comet thingmabob.

And BTW, do you know why Rogue Trader stopped being canon? it's quite odd actually.