easy to say but then I can't make a binary system and relative planets .
I would probably reformulate the rule from Gordon. Two planets orbiting the same star should not be close, otherwise the system will be unstable. But if they form a close double-planet (like Earth-Moon), then it is OK. How close should the planets be to maintain stability gives the so-called
Hill Sphere. If you have smaller star and the double planet is close to it, then the planets must be very close to each other, otherwise the star will disrupt them. (Which also implies they will be tidally-locked to each other.)
System of planets or moons around Gas Giant should be also pretty stable. You can look at this interesting post:
http://planetplanet.net/2014/05/13/building-the-ultimate-solar-system/ , where author describes how to make largest possible stable system.