I think it's important to keep the human aspect in focus, despite whatever 'relationships' are involved.
People are all their own masters, have various feelings & moods, make their own internal decisions etc daily. When any 2 or more people see themselves as some connected whole it threatens to cast a shadow over the individuals - that 'human' element.
In the end, we can never be (or take responsibility) for someone else's thoughts or actions. Things will unfold as they need to. We try to be aware of the interaction and not needlessly (or heedlessly) insert more complexity, but in the end, we are all just living the life as best we can figure out.
This isn't some cop-out. It's just reality. We do the best we know how, but in the end we're just being swept along by the winds of time like another leaf.