This is an extremely misleading statement. The Earth-Sun-Moon is a 3 body system and quite stable. Obviously moons and multi-planet systems are quite common. As

This is an extremely misleading statement. The Earth-Sun-Moon is a 3 body system and quite stable. Obviously moons and multi-planet systems are quite common. As are 3-star systems. Our nearest neighbor is one: Proxima/Alpha Centauri. And Proxima Centauri has a planet too. What is difficult to find stable solutions for is 3 body movements where the three objects are of similar mass. But that is an improbable circumstance to start with. Also that citation seems to be totally disregarding the fact that multi-body systems never start in stable systems but instead naturally align into them.