You do NOT include his income on your return.
Your son's W-2 income is below the filing threshold of $6300, so (assuming he has no other income) he is not required to file a tax return. However, he would need to file a return if he wanted a refund of any federal tax that was withheld from his pay.
If he does decide to file a return, make sure he indicates on it that someone else can claim him as a dependent.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
