spawning rigidbodies next to each other

I am trying to spawn units from a single spawner to the single point. They are all rigidbodies. What's happening right now is that they fly apart from each other when one is spawned on top of each other. What i want to happen is for new unit to appear as close to the spawn point as possible, as long as it is not on top of another unit. So they all neatly start spawning around the starting point.

Question is - how do i manage that, given that units can move more or less freely?