Thanks for your question! I suppose the larger issue has to do with whether this is emotionally, psychologically and interpersonally healthy. The questions we usually ask are: 1) Does the individual view this behavior as a problem? 2) Is it interfering with their lives in some way? Are there some negative consequences? 3) Is it interfering with the growth of healthy relationships, especially with one's partner? 4) Has the behavior become addictive and/or maladaptively used to deal with stress? 5) Are there spiritual or religious beliefs that play a role in the individual's perception of this behavior? Your question alludes to the issue that many couples struggle with; namely, does viewing pornography constitute "cheating" or being unfaithful. The answer to this lies within the relationship itself and the parties involved; in this case your parents. Some relationships tolerate this behavior and others don't. As this issue obviously bothers you, it may also bother your mother. Clearly however, it would be incumbent upon her to voice her concerns directly and consider individual and/or couples counseling if the issue was a serious one for her and wasn't being resolved. Likewise for your father, individual counseling may be an option if he views the behavior as problematic and he sees the need to stop viewing pornography. Clearly, this issue has many aspects to it that cannot be fully addressed in the context of this column. Ultimately, every one of us needs to search our hearts on this issue and decide how we will respond to the increasing proliferation of pornography in the society. Hope some of that helps you with your understanding.