What do you suppose the eldest son of the King family did that was so "dreadful"?

Towards the end of Chapter Four, Meg tells her family tells her family how she found "everyone in a flurry" over some "wicked thing" that the children's older brother had done. This resulted in his banishment from the family home, "Mrs King crying and Mr King talking very loud," and his sisters "turn[ing] away their faces when they passed [Meg]" to hide their tears. What do you think the son might have done to warrant such a reaction?