@AdamNe wrote:
If you are unmarried, your child lives with you, and you provide over 50% of the financial support for that child, you can claim him/her as a dependent and file as Head of Household.
I would not be confident in saying "he does not have to file anything" without having more intimate knowledge of the details. Every tax treaty is different.
There are actually 3 different sets of rules under which a diplomatic employee is exempt from US tax, only 1 of which involves bilateral tax treaties. See chapter 10 here,
https://www.irs.gov/pub/irs-pdf/p519.pdf
It would certainly be up to the individual to make sure they really do meet at least one of these sets of conditions.
