As per the chart, your son would have a high level of sharpness and intelligence. He would be an exceptional observer with good memory.
Further he could gradually start speaking with constant guidance and encouragement and could lead a normal life. Love and care can do wonders in life and with due care he would gradually become normal.
Have a professional therapy if required and keep him encouraging to speak and he would eventually pick up.
Karka Lagna with the Lagna lord Moon posited in the eleventh house and Rahu posited in the Lagna; Fourth lord Venus posited in the fourth house; Second lord Sun posited in the fifth house conjunct Jupiter and retrograde Mercury; Ashtakavarga scores of second and third houses are 33 and 39 respectively.