So I played some Retail FS2, read trough the Wiki concerning Shivans etc. and the Results/Facts are very clearly.
1. It is the Crab Nebula. History Section clearly states that.
2. The Crab Nebula is about 6000-7000 Lightyears from Sol (In Reality)...don´t know how far away it is in FS2.
3. The Ancients did not make the Shivans, BUT they have been build, not evoluted like Terrans or Vasudans did.
4. Some Informations state that the Shivans are either Insect or Cyborg Lifeforms.
5. The Shivans being controlled by a Hive Mind. So there must be either something like a Queen that controlls the Hive, or someone who builds them and now controlls them.
6. Shivans can´t life in Subspace, because they have Shields. In Subspace Shields are unusefull, so why should a Species living in Subspace, build Shields ?
7. The Shivans are Nomades. At least that part the GTVA meets in FS2, also in FS1.
8. Just because theyr Nomades, doesn´t says theyre in search for theyr Home Universe. They might be Nomades just as a Fact.
9. The Fact that Shivans create a Supernova without doubt, killing Billions of Lifes, interfers with the Solution they want to return to theyr Homes. A Species without Emotions and controlled by a Hive, doesn´t cares about theyr Homes (in my Opinion).
10. The Fact that they are ruthless and kill everything they met, does NOT interfere with the Fact, they creating Supernovas and killing everything inside a Star System. So they are simply bad$%&.
So for me the Solution is easy. There is another Kingdom, maybe a Dominion or something similar. And thoose are afraid of the Terran and Vasudan expansion into Subspace and the whole Galaxy. They send Shivans to simply cut of the Connections to theyr "Dominion" Star Systems.
I also read something in Wiki, that Shivans only act, if other Cultures are fighting each others. I support that Idea. If People are not willing to make Peace by themselfs, the Shivans create the ultimate Peace...in Death...
PS: The Ancients, though, might be the Creators of Shivans. And if Terrans extinct the Shivans and something even worth shows up, the Ancients, maybe, might still be around somewhere, evoluted to another Species that is even more horrible then booth, the Ancients and Shivans are.
PS2: Anyone remembers Steven Kings Langoliers or Species 8072 from ST Voyager. Thoose that came to "clean up" the World. Pretty much fits to the Shivan Theme, doesn´t it...