Remember that children already know something is wrong between mother and father. They may not know the facts but they know something. If the infidelity has never been revealed openly, later in life they may tell their therapist that they suspected that their parent had an affair(s) but they have no proof. Young children are too immature to be able to consciously deal with a betrayal of trust of this level. However an older child can be deeply damaged by continuing with a lie that is clearly a lie to everyone involved. A while back I worked with a family whose father/husband had an affair that lasted several years. Although the the marriage ended and he began living with his girl friend he continued to lie to his children about the affair. Everyone “knew” but he refused come clean with the truth. His oldest daughter, age 14, begged him to tell the truth and he still persisted in lying. His daughter’s anger and sense of betrayal increased with time. Finally her father brought her to therapy. When asked what she was so angry about she said that she hated her father for lying and felt totally abandoned by him. I then asked her father to have a few private moments with me and suggested that he tell his daughter the truth about the affair and ask her forgiveness for lying. He did so and his daughter was visibly relieved. I received a call several weeks later from him. He told me that his daughter had changed for he better and the tension between them was replaced by better feelings and cooperative behavior. Tell the truth when you know that your lie is hurting another.