In Knight of Shadows we see that Borel (Logrus ghost) knows about Jurt (when Merlin and Jurt walk to the broken pattern):
...There were a number of them—roses of many sorts. I stopped and picked one up. Its color was almost silver…
"What are you doing here, dear boy?" I heard a familiar voice say. I straightened immediately, to see that the tall dark figure which had emerged from behind the block of ice was not addressing me. He was nodding to Jurt, smiling.
"A fool's errand, I'm sure," Jurt replied.
"And this must be the fool," the other responded, plucking that damnable flower.
"Silver rose of Amber—Lord Corwin's, I believe. Hello, Merlin. Looking for your father?" ...
The speaker was Lord Borel, a duke of the royal House of Swayvill and reputedly one of my mother's lovers of long ago.
So how can that be? Merlin was the first son of Dara. Later Dara married Sawall. At this point Borel is dead, and only after that Despil and Jurt are born. The only possible explanation is that Logrus somehow implanted that knowledge in Borel's mind. We can see that "implanted" memory in case of Caine's ghost:
Caine: "And this other one—his name is Jurt, isn't it?"
He gestured toward my brother, who had just gotten to his feet.
"How do you know that?" I asked.
He halted, furrowing his brow, narrowing his eyes. "I—I'm not certain," he said then.
Caine seems to be puzzled about that part of his memory, but in case of Borel it looks like he knows Jurt very well.
So what actually happened?