As the saying goes, two is a company, three is a crowd. But, hey, I have to admit that the three can pack punches!
Consider if there are two little pigs rather than three. Or, only two bears to scare Goldilocks away. Would the stories have worked as well? I doubt so, though I could still picture the two bears kicking Goldilock’s butt. Using the rule of three, one creates tension, builds the tension and then releases it.
Rule of three is one of the easiest writing tool. Admittedly, at times I can get too carried away with it! Time to start breaking the rule…