People ..

I would characterize people into five kinds, Aloof, Dependant, , Protective, Independent, Co-dependent.
The kinds of people you feel inclined to interact with depends on the type most complementary to yours.

Aloof by definition prefer no interaction. They are in a world of their own and need no external stimuli.
Protectors have a need to feel good about themselves, to protect, to control, to have power and this is a perfect complement for the Dependent. They naturally they gyrate towards one another both reinforcing and fuelling their current life positions.
Independent people hate being chained down and prefer to seeks others of their type. Each free to do as they please, no explanations.
Co-dependent are the next form of independent who can be independent when they need to be but prefer dependence by choice - finding coexistence is far more satisfying due to they synergy of co-existence.

Of times the same person has a different relationship with different people (potentially dependence/protective with parents/kids, independent/co-dependent/aloof at work, codependent with spouse etc.)
With time people evolve, they grow/out-grow various traits and unless their counter part change in a complementary way, people break existing bonds and forge new ones. This is probably how we leave behind old friends and make new ones. As we grow we out-grown the co-dependence on our old friends and the relationship changes to a different flavors which is not so much to our taste.

What makes things more interesting is that within the same two people the relationship may vary with the time and circumstances and that is the mark of a strong bond - it has not one but multi-links. Its when two people can grown/alter/evolve in sync. When I am Independent or Aloof the other lets me just be, when I am Weak the other is there to Protect me and when I want to co-exist so also he/she.