Unfortunately, this is sometimes true.
Years ago, when I was teaching high school seniors, I had two high-achieving students who, becuause of the small size of the elective class, were constantly in group projects together. They agreed on NOTHING. They were constantly sparring; I had to keep tossing them out of the classroom or they would have argued well into after school hours.
This went on for almost the entire year, until May, when they came into class holding hands.
They’ve been married forever now, and have eight children. Go figure.