How do I pick an object that has another object nearby?

I've been scratching my head for a while now and i cant figure out how to do this.

I want to pick every object on screen that has another object within a certain distance. Whenever objects get clumped together i want to change some attributes.

Pick by comparison: distance(block.X,block.Y,Family1.X,Family1.Y) < 120

didnt work at all.

Any ideas?

What are you up to? Boids ? Or something else? A picture will help people to understand the case.

Maybe using another object as area of collision?

What are you up to? Boids ? Or something else? A picture will help people to understand the case.

Im trying to optimize my Z Ordering routine to use less CPU for mobile, so I only want to sort objects that are nearby or overlapping. I don't want to create a lot of dummy sprites to limit the sorting to the ones that are overlapping, so i figured i would use distance instead. So what i need to do is to pick every sprite that is near another sprite, because theres no point to sort sprites that are not overlapping in any way.

Why not just use the "is overlapping" condition, if that is the only thing you are interested in?

Because the collision boxes are not set at the outer limits of the sprites, it would be awesome if there was a way to check for any colliding BBbox instead.

just an idea, have you tried, "for each block" pick by comparison...