Looking for an old children’s book.

So long story short there's this book that I've been looking for for ages and I can't seem to remember the name of it.

The story is about this little girl who's trying to get her little brother to go to sleep because he's a baby and he won't go to bed. The characters are African American little boy and girl. And like I remember her distinctively saying good night baby brother or something along those lines and like she's just trying to get him to go to sleep in the whole entire book is literally her telling him a story to get him to go to sleep. She's annoyed with him by all means because she's like five or four or something and the baby is literally a top over younger.

I remember it having like this very blue overall tone to it the book itself was blue and the little girl had pigtails like doc McStuffins and she was wearing a little light blue night gown I think in the baby brother was in his crib.

But I do know the book is blue itself and I thought it was something along the lines of goodnight Moon or something like that but it's not.