I think one of the biggest issues everyone glosses over is … we change during our lifetimes.
We are not the same person in our 20s, our 30s, our 40s for all kinds of reasons … our work, our situations, events in our lives, trauma, biological changes, genetics or just psychological changes. Some people stay the same sexually and stay the same throughout their lives, whether its being straight, bi, gay or anything else … I know some people who changed over time from being straight, to bi, to gay or to just asexual … in one way to another. I’m sure everyone know people like this. It’s human nature, most people are not born a simple being that stays the same forever, we evolve and change sometimes because we want to, we have to and other times against our will and biology.
So to have an ever changing pair of people living together … we should not expect them to stay the same forever and want to be together indefinitely.
But the inverse is also true too … maybe the two 20 year olds accept one another but change when they’re 30 … and now the 30 year olds now accept each other at this age … and on and on.