Most congenital anomalies are caused by genetic and mutations. Often time, multiple anomalies can occur at the same time.
Unfortunately, you son needs to be operated in the future. As of now, he/she may not show any symptomps as the blood flow move to the right side of the heart due to the holes. However, in the future this can cause cardiac and lung failure if left untreated for a long time. You need to google eisemenger syndrome.