What causes cheating and divorce in your opinion?

My grandparents and my parents and all my aunts and uncles except one stayed married and did not divorce. But all of my cousins are divorced or half divorced except the ones who never married or the ones who married PhD students and Chinese Ivy League graduates, people who are the top among 10,000 or 20,000 others. Or the ones who marry PhD professionals and professors.

What causes cheating and divorce in your opinion?
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