Final answer:
The concept illustrated in this scenario is Family Secrets, where the client discloses a hidden affair and child to her social worker.
Step-by-step explanation:
The family therapy concept that is illustrated in this scenario is Family Secrets. In this case, the client discloses a secret to her social worker, revealing that she had an affair and had a child as a result. This secret has been kept hidden from others, including the couple's child. Family secrets can have a significant impact on the dynamics and functioning of a family as they can create tension, distrust, and affect the emotional well-being of its members.