In an alternate universe, we have a spot in the Orion Arm where we have nine Earth-like planets orbiting three red giants. Judging from the size and luminosity of each star, it's been conferred that each of the stars has been a red giant for 542 million years, which means it doesn't have as much time left (although, as this article suggests, depending on the original solar mass, some red giants can live to twice as long as Earth's current age!)
This map is a basic simplification more on the structure than the distance. Essentially, the center of the system is a binary of red giants orbited by a third, solitary red giant.
I imagine that the binary orbits each other from a distance of four AUs, but is that far enough for the stars to orbit each other without crushing under their own gravitational weight? And how far would the third star have to orbit the binary to ensure both gravitational stability and a wide enough habitable zone for nine Earth-like planets?