My child minder told me today that she caught my 3 yr old ds putting a bean bag over 4 mth old dd's head then trying to sit on her. How do I get my ds to understand the severity of his actions and to stop. Is it normal for older siblings to NEVER leave baby siblings alone? He is constantly in her face and poking and proding her. It's driving me mad, I can't even go to the loo in case he tries to do something to her....