There is a common situation which can occur in which one person in a relationship is interested in sex and the other is not. Sexless relationships are extremely common and many go years without sexual intimacy. For one reason or another sex fades away until it is no longer happening at all.
I think infidelity is a fascinating topic because it has existed for as long as the construct of monogamous marriage. Most of us have been affected by it it some way. For example, maybe a partner had an affair, maybe you did? Maybe you were the one having a relationship with