We know, by the end of the book, that Gavilar talked to Taravangian about his visions and his plans.
> "He had taken the first major step toward unifying the world, as Gavilar had insisted would need to happen if they were to survive."
> "That was, at least, what the visions had proclaimed. Visions Gavilar had confided in him six years ago, the night of the Alethi king's death."
We know, by the end of the book, that Gavilar talked to Amaram about his visions and his plans.
> "It was happening. It was really happening. The Sons of Honor had, at long last, achieved their goal. Gavilar would be proud.
But we also know, from the fact that Dalinar didn't understand his visions and was confused by them, that Gavilar never confided in Dalinar. And we know, from the fact that Navani didn't understand his visions and was confused by them, that Gavilar never confided in Navani. Why did Gavilar decline to confide in his immediate family about something this important and critical?