Ask the Yakuts and the Anatolian Turks. (: Gagauz and Uzbek might be an even more apt real world example, as both speak Oghuz dialects, and there’s a significant gap of non-Turkic speakers in between them (Persians).
In the specific case of this gameworld… care for a bit of loredump? Before the age of “Hegemony vs Empire” there were centuries of migration back and forth across the rugged Erezziano Isthmus, with Halassurq-speaking peoples coming from the vast eastern continent and the ancestors of today’s Shayardenes and Erezziano pushing up from the coast of the smaller continent.
One of the most successful groups of mounted Halassurqs fought their way all across the isthmus, sacking as they went, until they came to the great plains north of Aveche and established themselves there as pastoralists. The handful of settlements they left behind on the isthmus were conquered or assimilated over the years… but the Nyr pastoralists expanded to fill the whole northern peninsula, periodically plundering the neighboring agriculturalists and building grand but sparsely populated cities along the spine of hills in the middle.
Indeed, their expansion didn’t stop at the borders of today’s Nyryal and the Hegemony… while the cold reach west of the great firth never supported many settlements, some exiles of the Nyr pressed on between the wasteland and the mountains until they once again reached habitable grasslands. Those tribes, descended from the kinslayer Brurq, dominated and intermingled with the previous inhabitants of that area. The land came to be known as Brorach and its people as the Broracha – a savage folk, prone to cannibalism and Goety, whose language was nonetheless still recognizably related to Halassurq.
Back in the northern plains of Nyryal, the Nyr increasingly preferred trade to plunder. The coastal city of Umri, where they received trading ships from their newly Imperial cousins in Halassur, became the cultural and intellectual capital of the Nyr tribes. Glorious Nyrnakan remained the political capital, where the great coalitions of families gathered once a year to agree on things like migration routes, trade policies, and the occasional conquest. It was also the religious capital, home of the gods who had sustained the Nyr through all their wanderings.
The last Great Gathering of families in the (by then) Nyrnakan Republic was to agree to ally all the Nyrish tribes to their cousins in the Halassurq Empire. This meant war against the fast-expanding Karagonds, who had clearly set their sights on the whole continent, not just Erezza and Shayard. (And also to hear a different proposal from a Nyr prince who… but no, that lore won’t feature until a much later game, so I probably shouldn’t even hint at it this far in advance.)
Unfortunately, the Halassurqs were unable to make progress up the isthmus toward Karagon, so the Nyr were left to fight largely alone. They held their own for a while, but after a decade of war the Thaumatarch Hera dropped a mountain on Nyrnakan, marking the end of Nyrish liberties (and religion). Forty years after that, the Broracha’s infamous Goety catastrophically backfired, creating the Xaos-Lands… and leaving Halassur with no independent allies against the Hegemony.
@Deathless, some Nyr today (or Neres, to the average Shayardene) would welcome an invasion by their linguistic kin. However, most contemporary Nyr are not particularly attracted to Halassurq culture – which is by comparison to their own very religious, very gendered, very centralized, and very agrarian – and wouldn’t see much to prefer in the Empire compared to the Hegemony. Indeed, some of the Hegemony’s most successful generals against Halassur over their centuries-long conflict have been Nyrish.