By custom and law, the Kimdori don't actively take sides in the wars of other civilizations. They've been known to work on both sides of a conflict.
This'd probably be a massive spoiler, but as you know...if you ask the question, clearly you're ready for the answer. Specifically because these questions keep coming up over and over, lol.
The Faey are indeed the mythical elves of British and Celtic folklore. The Kimdori, on the other hand, are not "were-wolves." There were no Kimdori on Earth until Kiaari came. This is why all the human telepaths descend from a particular place, and from a particular time. The Faey were mistaken for elves, they interbred with the human population, and then they died out, passing their genetic line down into their descendants.
I've already revealed why they came to Earth to some, so may as well put it out here for everyone who reads this. The Faey that came to Earth were the remnants of the House of Karinne, fleeing the war and the systematic extermination they faced at the hands of the noble houses on BOTH sides of the war...because Karinne was a very small house, filled with scientists, philosophers, and doctors. They had no army, no warships, nothing but a small planet that was their own, and to them, the war had no importance or meaning. So, they refused to take sides. And naturally, Faey being Faey, BOTH sides of the war decided that they were the enemy. The House of Karinne was the first of the noble houses to be destroyed in the war. Their planet Karis was rendered uninhabitable and the entire population wiped out, destroyed by House Merrane...which is the current noble house that holds power. Empress Dahnai is a Merrane.
Those Karinne not on Karis, scattered through the Faey planets, were hunted down and killed. Merrane took what little assets that Karinne had, and House Karinne came to be no more.
A handful of Karinnes not on Karis survived the eradication of the house and were too far away to be reached by assassins, a research expedition conducting research on a distant planet, a planet at the rim of space explored by the Faey, with no spacefaring race beyond to claim it...open space. Instead of returning to Faey society and going into hiding, they decided to simply leave the Imperium and take their chances out in the wilderness. So they took their ship and left, heading out into that unexplored space.
And they eventually found Earth.
They landed in southwest Scotland, in an uninhabited region of the lowlands that's now called Dumfries, and they took immediate steps to ensure that they'd never be found if their enemies came looking. Everyone else thought they were dead, and they were very careful not to give away the fact that they weren't. They landed on Earth, left everything behind (even their clothes), and then sent their ship up on autopilot to fly into the sun, leaving absolutely no trace that Faey had ever landed on Earth except for the Faey themselves, who immediately went into hiding. They came to Earth with absolutely nothing.
There were 67 Faey in that ship. They were the nobles, researchers, scientists, and the support crew and workers that had been with them. Given that these Faey were well versed in both science and "roughing it" out in alien ecosystems, they managed to survive, even thrive, in their new environment. They kept to themselves, avoiding the native population, but that isolation eventually broke down over time, as the fear of a Faey warship appearing in the sky lessened over time, and they came to know that they were safe. They began to interact with humans, and then intermarried. Eventually, the pure lines of the Faey died out, leaving only their crossbreed descendants behind.
Of curious note is the melding of human and Faey genetics. Human appearance genes are totally dominant over Faey genes, which caused every child born to a Faey and a human to appear completely human. But on the other hand, every one of them had telepathic ability, for the genetic footprint for talent was a dominant trait.
Every telepath on Earth descended from these 67 Faey. Some, like Tim and Temika, share a common "alpha" Faey ancestor, and have quite a few people in their extended geneaology. There's a few thousand men and women that also share the same alpha ancestor that Tim and Temika do. Others, like Jason, are the only ones of their line left. Jason is the last living human descendent of his alpha ancestor, and his ancestor was a member of the Karinne nobility.
Jason is in the same family tree as Gora Karinne. Jason is descended from Gora's younger brother, so he and Gora share common lineage in Gora's parents.
And Jason's "sister?" Well, she's real enough, and also of Jason's line, descended from Gora's older brother, who married a Merrane noble and had children, but died before the war began. The sister Miaari told him would appear is a Faey descendent of Jason's root ancestry, a noble in another house. She's a Merrane; and no, she's not the Empress, so don't go there. She's just one of the tens of thousands of Merrane nobles, a minor noble in title only that works for the Imperial government, but she's unique the same way Jason is. She's one of the last descendents of the Karinne nobles.
And Jason will sense her the same way he senses Kimdori. That is how he will know her.
Jason's unique ability to sense Kimdori isn't normal among Faey, and as most suspect, does involve the Kimdori. Jason doesn't have a Kimdori ancestor, but we can say that the Kimdori did have something of a hand in his family line that caused them to develop this ability. The House Karinne and the Kimdori were bound together in many ways, as the Kimdori were helped by the science of Karinne, and Karinne earned the respect and friendship of the Kimdori in return. The reason they're helping him is tied up in this. The Kimdori feel that they owe a great debt to Jason's family, a debt that they thought would never be paid after Karinne was destroyed. Helping Jason now is a way to repay that debt, but they can't overstep their own laws, as well as oaths and agreements they have with other houses in the Imperium, and the Imperium itself. They can't directly interfere, so they're doing their damndest to indirectly interfere.
And there you go. Questions answered.
Just another guy from the shallow end of the gene pool.
Read Fel's post if you haven't done so yet!!