L4 and L5 are stable when the smaller mass is less than about 0.0385 times the larger mass [1]. This means e.g. a typical binary star system would not have stable L4/L5 points. The reference [1] works through this in careful detail and is an excellent reference on this topic.
[1] Solar System Dynamics, Murray and Dermott, Cambridge University Press.
[1] Solar System Dynamics, Murray and Dermott, Cambridge University Press.