Jim, I think you're asking for trouble (astronomically speaking) at least with your scale. [Light Year - ly] Proxima Centauri (4.25 ly) and Alpha Centauri (4.35 ly) are pretty close to our sun (for perspective). But we are fortunate that we are no closer than than that.
Consider these numbers. You are no doubt familiar with the Kuiper Belt, where many of our comets come from, extends out as far as 2 ly from our sun. That is as far as our suns gravity influence is known to extend. If you put another star within 1 ly, for a long time, that star won't be there for long unless it has a very specific orbit that keeps it from crashing into our sun, which makes it a double star. Now if you add a third star to the original 2, there is no known solution to that problem, but the effects are likely to result in just 2 stars really soon. My point is that I don't think that 2 stars, that are too close, would last that long, unless they are orbiting each other. Then there would be other problems in planet formation (a different view appears later).
Think about denser areas of stars and dust. The Orion Nebula, filthy with dirt, its 28 Light Years across; embedded in a spiral arm. A star system there would get pummeled with comets, asteroids, and no doubt bad TV shows for years. The Hercules Cluster, 10,000 of stars densely packed within 160 Light years; no doubt lots of gas as planetoids in between. Lots of fireworks, no doubt. So you can't have these areas for older civilizations to form.
Some of these Goldilocks zones are really probabilities for being able to survive without getting hit by comets and the like. You don't have to be in a Goldilocks zone to beat the odds. Other Goldilocks zones (like for radiation) you won't beat.
Gravity gets us all in the end. Andromeda and the Milky Way are going to collide, and we are 2.5 Million Light Years apart.
Earth actually has a big advantage with having Jupiter as a big sister in our solar system. Earth would have been hit with many more life/species ending events if not for Jupiter (and probably Saturn) sweeping out many of the space junk and catching stray comets/asteroids that come in from the Oort Cloud and Kuiper Belt.
Remember Shoemaker-Levy 9?
https://www.google.com/url?sa=t&rct=...cK4SX0Gsqo1a_n
That's compliments of Big Sister protecting the siblings.
Larry
DevilHorse