The long-term solution may be to reach a consensus that infidelity is the lying, not the physical part. A lot of people, including myself, subscribe to the theory that sex, drugs, and a part of the reaction one has to rock & roll (or dance, classical, any other type of music) is every bit as deterministic as what will occur in the seconds after a big shot of hydromorphone, and as drugs are tools and by themselves -- there is no moral valance or content.
If one is in a relationship with a member/s of the opposite and/or same sex, it has to do with personal growth, building different levels of society like the family, neighbourhood, community, and so on. It would be good for society and the people involved to remove the parts of it having to do with control, stasis, and jealousy. It can be hard, and it is a dialectical and very much involved process which can take many years and lots of work and manifestly few people reach a point that really helps themselves and the others around them.