Saí da minha cópia para responder a esta.
Para responder à sua pergunta se isso for explicitamente contido no livro, sim, é , mas um pouco obscuro. Provavelmente, para mantê-lo como uma revelação para todos aqueles que não perceberam imediatamente.
The passage is on page 243:
A boy-child cowered, and slithered away on his back, clutching at a great shield and an axe too big for him to lift. The Bloody-Nine laughed at his fear, teeth bared bright and smiling. A tiny voice seemed to whisper for restraint, but the Bloody-Nine hardly heard it. His sword hard-swung split big shield and small boy together and sprayed blood across the dirt and the stone and the stricken faces of the men watching.
(Emphasis mine)
There is no name given in this passage, but it’s clear the Bloody-Nine has done something horrible by all accounts and Logen even tried to hold him back but failed.
Then later on page 319:
Especially not the man who killed my son, eh? Logen felt himself go cold, from the roots of his hair to the tips of his fingers. What did you think? That I wouldn’t know? The hillman leaned back to look Logen in the eye. You slaughtered him before the whole world, now, didn’t you? You butchered little Rond like a sheep for the pot, and him just as helpless as one.
(Emphasis mine)
The earlier passage doesn’t specifically state that this boy is Crummock’s son, but it can be assumed that only his son would partake in the battle and could be described as a boy-child.
There are also Crummock’s other comments. That he was slaughtered like a helpless sheep (the boy clutching his shield while trying to get away on his back) and having been killed “before the whole world” (the men watching the scene with stricken faces and getting sprayed with the boy’s blood).
Took another look into the book because of Duralumin's comment. Together with this passage it becomes very clear that Logen killed Crummock's son during the battle. Here Crummock and his three children are first introduced.
Page 95:
A little boy came next. He had a round shield across his back, much too wide for him, and a great axe he was lugging along in both hands.
(Emphasis mine)
Quanto à pergunta se Logen não percebeu ou não se lembrou. Logen e os Bloody-Nine não são exatamente a mesma pessoa. Ele muitas vezes não lembra o que aconteceu quando ele se torna o Nove Sangrento. Pelo menos não totalmente. Afinal de contas ...
Page 255:
He wanted to weep. For the death of a good man. For the fact that he might've been the one to cause it.
He doesn't seem to remember killing one of his closest companions, but he seems to suspect that he did.
E o Bloody-Nine simplesmente não se importa.