Fili knew the pain that his brother felt, and by looking back at Saeril, he could tell that something unlikely happened, and conflict took place between them. He was just about to say something, when he no longer felt his baby brother following him. Turning back, Kili was being held back by Thorin. Disbelief filled him that their uncle would split them up. Never in their childhood, have they ever split up; it was impossible. Right now, he felt despair for the first time. 

"Uncle, don't do this!", the elder brother jumped to Kili's defense. "We grew up on the tales of the Mountain, tales you told us; you can't take that away from him!", Fili narrowed his eyes at Thorin and went to get out of the boat to stand with his brother. "If you won't let him go, I stay. With him and Delva." 

Saeril looked up from her devastating period when she heard an argument amongst Thorin and the brothers. To top it off, Kili looked saddened. What was going on? What did Thorin say to them? Curiousity, guilt, and concern filled her, making her stand from where she sat.