They may be asked to keep secrets and/or expected to chose sides.
Asking a child, overtly or covertly, to take a side is like asking a child to lose that parent. Keeping secrets from one or both parents can create a terrible guilt and sense of self as destructive.
There are reactions that occur while the affair is going on, but before it is disclosed, and reactions once an affair has been disclosed.
They are extremely sensitive to hypocrisy; when a parent’s actions are exposed as opposed to his or her stated values that parent falls off a pedestal.
And when a parent falls off of the pedestal it changes the child’s whole conception of who their family is and thus, their sense of who they are.
The older a child is, the more capable he or she is of abstract thinking, so worries about what is going to happen to the family and how their lives will change or who they will lose if there is a divorce can surface.
They may withdraw or act out in an effort to get their parent’s attention, stop the affair, or prevent a divorce.
Other couples are in complete denial that the children are effected at all; since the children are showing a lot of support and understanding.