It's not suitable. Such stories are not acceptable in general society as they can make people uncomfortable and violate the norms of propriety. We should focus on positive, healthy relationship stories instead.
Literature is often expected to convey positive values, emotions, and intellectual stimulation. Erotic stories about couples may not meet these criteria. However, in some specific literary works that are aimed at a more mature and restricted audience, there might be some exploration of sexual relationships within the context of a greater story about love, power, and human nature, but this is still a very controversial area.
Trust can be a non - erotic element. For example, a couple who trust each other completely. When one of them has a career change opportunity that involves some risks, the other one fully supports without hesitation because of the trust they have in each other.
Imagine a couple on a blind date in a restaurant. They are both a bit nervous at first. The woman might be fiddling with her napkin and the man is trying to break the ice with some small talk about the decor of the restaurant. As they start to relax, they find out they have a common interest in a particular type of music. They end up having a great time, chatting away and sharing a dessert, looking forward to a second date.
Once upon a time, there was an old couple and a young couple living in the same neighborhood. The old couple had a beautiful garden. They often shared their gardening tips with the young couple. The young couple, in turn, helped the old couple with their new electronic devices. They would often have picnics together in the park, sharing stories and laughter, creating a harmonious and friendly relationship.