I grew up with this guy who was a good person and actually pretty decent looking, but didn't really seek out girls. He didn't have the confidence. All the moms would always ask us girls why none of us showed interest in him. First of all, many of us only saw him like a brother. Secondly, we didn't want to settle or be someone he settled with.
Years later after many of us got married, he actually married one of our younger sisters who was a homebody, plain, and didn't have any boyfriends. It seemed like all his options were running out. Again, they were familiar with each other so it was easy to just settle with each other. Lo and behold, some time after they had children he cheated with a divorcee. Back then the divorcee wouldn't have given him a chance because she was pretty, popular, and had a lot of boyfriends. But after divorcing and moving back to town, I guess no guy really looked her up despite her still looking very attractive. She was known as a poj laib so the men didn't quite care about her anymore. Now that she was easier for this guy to pursue, he sure got her good. Again, he is a decent looking guy (not fat) and a good husband. This divorcee finally saw him for that after her failed marriage to a laib guy. Our younger sister (not really a sister but that's how we view her) nearly had a heart attack. She fell into a state of depression and now has some PTSD.
Proximity and familiarity make it easy for people to fall into a relationship but they aren't really in love with each other. They are together because they are like an old t-shirt to each other. Sure, it's the first shirt they grab but they also don't miss it when it's gone. Their heart just isn't with you. They're with you because you are just what they're used to, not what they truly desire.