Please don’t let them put you off. The fact that you’re already concerned proves that you would be more pro-active in not allowing this to happen. You’re already looking out for a baby you don’t have.
Also, I wouldn’t say this is normal toddler behaviour. Yes, it happens but Ocean has been allowed to do this and her parents pulling out their cameras is teaching her this is acceptable behaviour. If that’s what they film, imagine what they don’t film.
I’ve got a 7 year old, 4 year old, 2 year old and 5 month old baby. I’ve done the toddler thing and the sibling rivalry thing lots. Trust me, if you tell them not to and you teach them that’s wrong that will learn to be gentle.