Hello--one of my favorites from the 1940's/50's is titled "Guess Who Lives Here?" illustrated by the beloved Eloise Wilkin, LGB #60. The milkman is one of the characters described with clues as to who he is, and then text reads "Guess who it is?"; next page, "he's the milkman" with a picture of him delivering milk to the family's home. My granddaughters were recently introduced to this "guessing" story, and they loved it (though it took a bit of explaining about milkmen and their function in bygone days). The family has a little boy named Terry and a baby sister, unnamed in the story. Is this the one? Hope this helps!