My baby is turning one, would small fit him? He is 28 lbs

No I don't believe so. I purchased a small for my nephew who is turning 6 years old. :-/

My son is 9 years, 90 pounds. Size Large fit hi

I bought a small for my son who was 7 years old and about 50 pounds at the time. The label said fits size 4-6. I'm not sure what size the large says it fits, but hopefully this information will help you gauge. It is a great costume and he was the best dressed "king" in the pageant. Good luck!

Would a size small fit a 3 year old?

a medium fit a nine year old with plenty of room to spare. It was nice quality until he wore it playing around for a couple of weeks. The robe is long.

my grandson weighs 40 lbs and is 43inches tall is the small size going to be to small, should I go with medium?

Dont recall what size my son had, but likely a large. Go with the medium. My son probably was probably 52" and 100 lbs when he wore his. I thought the costume was a good value.