The history of the federation for the most part have always been a fight between the aggressive xenos against the civilized "democratic" federation. Almost all xeno civilizations that are mention in the history books are either gone or displace to the edges of the galaxy. However there are a few alien species that not only been spared by the wrath of the federation but essentially become integrated citizens, but the road for citizenship was rough and bloody. Today we will discuss the brief histories of each specie ascension to become members of a large galactic empire. Though I will promise that a longer more detail story about each species would come at a later time.
The Xermes would become the first race to be "integrated" into the Federation, a bird-like species from the arid world of Xerta, this race value in traditions, divided into several clans only barely reaching to their bronze age. The arrival of the Federation would only spell doom to their people as they were been exterminated, only the courage of a single warrior brought the clans together to make a last stand. But fearing the end of their species, Xerme clan leaders joined together to sue for peace, which it ultimately saved their kind.
The Rasorians were a somewhat similar story, hailing from the large earth-like planet of Podromos, they are a giant rhino-like species that are very strong and resilient but are also not very fast runners. Nevertheless the Rasorians valued strength above all else which this translated to many conflicts as they expanded across the globe reaching to the early medieval age by the time the federation arrives, their arrival cause most kingdoms to see them as "sky demons". The war was short lived as the federation technology surpassed anything the Rasorian could ever dream off, only a few remaining Rasorian kingdoms submitted to the federation while the rest were laid to waste.
The Dorbels is a different story, coming from a tropical moon of Durbin, they are a very small humanoid species that for most of their history were enslaved by a dominant insect-like species known as the Kri Kri that was experiencing a Renaissance age. Though the Federation would had just left this world alone it was by an accident that consequently lead the federation to start a rebellion that ended with the liberation of the dorbel people and the subsequent end of the Kri Kri, because of this the Dorbels were delighted to join their "liberators" federation.
And lastly we have the particular story of the Xi' ian, a jellyfish-like species that reside in the cold gas planet of Uva. What made this species very particular is that they were originally animals floating in a gas planet, only until an experiment by a scientist of whether this species could be uplifted that cause the Xi' ians to become intelligent. Since this move was highly controversial to the federation, that the Xi' ian were indoctrinated to become members of the federation, the Xi' ians would become the first and proably the last species to ever become uplifted by the federation in the forcible future. However the Xi’ Ian people have always had a favorable few to the Federation ever since of their uplifting, seeing them as a society of enlightenment.