Here you can see Jnr standing over the chick who is trying to keep a low profile. Jnr is a 4 year old son of Renee and half brother of the chick.
Here you can see Renee arriving with food for the chick but has to get around Jnr.
It seems that Jnr has freedom to intimidate the chicks as he is a higher status than them.
I have seen this before when Missys chick was attacked by a more senior relative and rolled over on its back, Missy instead of defending it just walked up and put food into its beak.