Rosalyn and Moe were Calvin's adversaries for different reasons -- Moe because he was a big-but-dumb schoolyard bully, and Rosalyn because she simply had no patience for Calvin's antics. Rosalyn was kind of like an older version of Susie. Waterston clearly had great affection for Susie -- IIRC he said he patterned her after his wife.

The strip definitely wasn't big on realism -- after all, the central relationship was between Calvin and his stuffed toy tiger, who he fancied to be an actual, live companion. And I suppose Calvin's parents did, in their own way, recognize what a pill he was. Calvin's father repeatedly made references to wanting a daschshund rather than a child, while Calvin's mother was known to make occasional, half-joking reflections such as, "[Calvin], anybody but your biological mother would have left you to the wolves long ago."