How to convince my four year old I am having a baby boy?

I think once the baby gets here she'll be fine with him. My four year old daughter swears up and down that she's a boy because she has two older brothers. I think it's an age thing. Maybe you could assign her a special duty when her baby brother comes, hopefully it will make her bond with him and then she won't care that it's a boy. Most hospitals usually offer a new sibling class. I know you said that she has other siblings but maybe if you let her take this class and ask the instructor ahead of time she could help get your daughter excited over her baby brother.