More like they didn't get any parental care, it's obvious the boy needs to let his emotions out when he's getting the crap beaten out of him, too bad his lashing out wasn't guided in the right direction.
Neither children, the sister nor the brother, are bad people in this case imo, they just had terrible upbringing and care, and that's way, way more sad.
This chapter was really immaculate in terms of art and battle, it was flawlessly beautiful.
It didn't need to be impressively drawn, it's just very cleanly done, great stuff.