There are many factors that do not have to do with common interests like how loyal one is to the other. Both can have completely different interests but they are steadfast loyal to their interests and that is somewhat applied to their relationships as well. There's also people that interests they are too embarrassed to express in public but do so secretly with their loved ones that are more open about those interests.
There is a lot of possibilities in the world, people these days seem to forget there is a gray area, and also don't know there are multiple factors rather than just one observable one
It's very much possible. Opposites attract. And if you look at some couples, you can see the differences of each other, whether very [different] or not. In my own relationship, he and I have little in common. He likes sports, I don't. He likes rap [primarily listens to], I don't. I like anime, he doesn't. He loves most food, I do not. He's sociable and easygoing, I'm not honestly. The list goes on. We've been together for over a year now and still love each other and talk all the time.
I know someone who would practically give their life for their partner, but they have so little in common and I don't see how they wouldn't get bored of each other or anything. They talk all day every day, whether it's the same topic over and over or just nothing of importance. It just puzzles me and I'm curious on other people's thoughts on the matter.