Infidelity in Marriage

Infidelity is defined as being untruthful to you partner or to your spouse. There are legal measures to deal with infidelity and it could be different from one country to another and from one culture to another. But all in all, behind all the legal battles and all the paperwork, the couple has to deal with infidelity on their own. One person has committed a mistake and the other has to deal with the mistake, or does he/she need to?