I will go out on a limb and say that cheating almost always is more than just sexual curiosity to try something different. It involves a significant dissatisfaction with the relationship, and this not just sexual. The cheater does not like the committed partner for whatever reason. It does not mean there are no feelings there, it just means there is enough negative emotion to push towards cheating. Men do it, women do it. I have done it. I learned very, very hard lessons, and I speak from personal experience. I vowed to never get into a serious relationship with a lady that did not include very honest telling of feelings and needs. Yes, there are relationships where communication has died. Now is the time to assess if it is worth saving, getting the help needed, and making real, sincere changes for both parties. If this cannot happen, then break it off and be done. Society frowns on divorce, but sometimes divorce is a relief for both parties. Each can learn and grow and start fresh. When kids are involved, it hurts them, but chances are they already could feel the negativity that was there in their parent's marriage. Kids see all.
In some societies it is understood that married people sometimes have affairs, but keep their marriages. I cannot personally fathom this, but I know it happens. It seems to me that both people would need to have this understanding up front.