We are all relatives of Adam and Eve and since 'relative' is a transitive relation we are all related to each other only to different extents. Human society and cultures weave amazing designs with relationships. There are plenty of aesthetic and real benefits from nurturing relationships. There are four key ingredients in a relationship - the objectivity and subjectivity of the two entities (people) involved. We have to be careful and rational in handling those four elements to retain or build any relationship.
A relationship it will last as long as both people involved in it find it useful in their own ways. Things get dull if their ways are almost identical and things get too messy if their ways are too different. But how do we know for sure how different two are and which is the best combination? Experimentation is inevitable and it is not wrong. Both the parties should be independent and be willing to participate in the experiments of building the relationship. There are protocols to be followed in the experiments. The protocols ensure safety simultaneously leaving some room for creativity. Different cultures have different protocols. So when we encounter change in cultures it might be a bit hard to decide which protocol to follow. But to keep things effective in life it's better to follow one's native cultures.
The usefulness of a relationship is usually both objective and subjective. The objective benefits can be easily made to be mutally win-win case by clearly and honestly applying logic. The unsurmountable problems come of course with little surprise from subjectivity. But we donot know how problematic subjectivity is until we build the relationship. If we find that subjectivity is too much of a problem then both parties can focus on objective part and limit their relationship to that level instead of ruining it. The best way not to ruin is stay away from the relationship. Don't overturn it making it bad to break it. That is just egoistic.