Relationships are action-reaction. Interaction. Causes and effects. Feedback. Any two things or ideas can be related and any thing or idea could be a relationship itself. The mind is fluid like that.
We often think of things as being made up of many relationships among relationships--an ecosystem for example. But we also see a system of relationships and convert it into a thing--a dog for example. This is akin to verbifying a noun or nounifying a verb. Relate your distinctions and distinguish your relationships! Have fun with it.
Nature has a way of hiding her relationships. You see the dog. You see the splash. The relationship is brief and tenuous, mostly invisible. But it is there. It is indeed a whole system, made up of parts!
The relationships you focus on--the one's you choose to recognize--are a function of your perspective.