Nagato's Six Paths of Pain and Summons: It is unknown how they got it. As for Nagato, some believe that he awakened it, and some believe that Tobi/Madara gave it to him. And Madara awakened his.
All I've seen from the Manga is that you need a strong body to be able to contain a Bijuu -- at least for Kurama. That's actually the only reason why I came to my former conclusion. But maybe they can become Jinchuriki... who knows.
Even if they were to be trusted with a Bijuu... they probably wouldn't even have the ability to contain such power. The main reason on why the Uzumaki were chosen for such is because of their strong Life Force.