The inquiry hears notes made after a visit to the family home by Lancashire county council in August 2021.
Axel Rudakubana is reported as saying his father Alphonse hits eight-year-olds, talking about himself, and hits his brother Dion.
The inquiry hears their father, in his witness statement, says the allegations he hit his children were "false".
But he says he smacked them when they were fighting each other, including the use of a slipper, the inquiry hears.
Alphonse says in the statement he didn't threaten Axel with a knife, and that he has a "tendency to make false allegations".
Dion agrees his parents had "lost control" of him by 2019 onwards.
The inquiry hears he compared his brother to the "sociopath" from No Country for Old Men, who kills ten people over the course of the film.
"I watched it recently and it concerned me," he tells the inquiry.
He says during the last interaction he had with him in the summer of 2023, Axel threw a metal bottle at him, but luckily he had already closed the door.