Tierkreis uses an infinite worlds concept that's used all the time in fiction and is implied to be based on a theory of quantum mechanics: given non-determinism of quantum events there are only probabilistic outcomes, and each of these "exist" as a separate universe. In Tierkreis we see universes that have different "versions" of what is in the primary one. So everything started the same but went along different paths.
We don't know if this is at all how the million worlds in the original series works. All we knew is that there were different fantasy domains that had nothing to do with each other, and I would believe never had anything to do with each other. So no, I don't think that Tierkreis actually borrowed from Suikoden's "million worlds" at all here, but merely used a very common literary theme, far too common to call this a familiarity.
You're forgetting that there were blatantly two
separate Viki characters in two different Suikoden games. Both know of the same dimension (Old Viki's "home") but it is never implied that they're the same person nor are they even considered as such when the Stars of Destiny are involved. That's very much like in Tierkreis, where Stars of Destiny would bind to new world inhabitants and characters from other worlds wouldn't even have the same Star of Destiny bound to them in their own world. (Marica? being the Tenkai Star in one world but Marica being Tenei in the main world).
Then again, nobody has ever thought to question the old and new Suikoden teams about the entire Million World concept ever since Tierkreis came out. Konami isn't the most forthcoming with new Suikoden info anymore, which would likely come from the first real gap between two major games since the one between 3 and 4.