New baby book for siblings?

Br

Hello, all! I am pregnant with baby #2 and want to get a book for my 4 year old son about being a big brother! In your experience, what has been your favorite book?

Also, bonus points for anyone who can point me to a book for my 6 year old step-daughter, who's already a big sister on her mom's side. Maybe a "big sister again" book?

Thank you so much for your help! 💕