What does it mean to dream of your parent cheating on the other?

The persons and objects seen in dreams are often metaphors or symbols representing something else. These symbols can be unique to each individual dreamer. For example, the mother and father in this dream could be symbols for two owners of a business, particularly if the dreamer is an employee of that business. In that case, one partner might be involved in shady business practices, or "cheating." ... A different possibility might be that the mother and father represent aspects of the dreamer's personality. The dreamer might be fully respectable in most areas but engaged in "cheating" in one part of life.

Any thing you dream more than once means affirmation. This means that God is trying to emphasis on it so as to raise your faith or for you to pray against it if it is negative.