Is there a way to detect collision of 2 instance of a same object (other than creating a new family)

It's been years that I struggle with that and I find the solution of creating a new family really annoying and unsuited for big project... Is there some other way ? A plugin maybe ?

You can detect collision with object A collides with object A, the problem is the picking and applying actions after this. There is pick nth instance you can use 0 and 1 but there's no guarantee of picking either one, I think it's done by lowest UID.

This is annoying… Do you know how other engine deal with it ?