the instructions for determinign a qualifying child are:
Step 1:
1. he is mine and my wifes son. yes
2. he was under 19 in 2016. yes
3. he didn't provide for over half his own support. no
4. he isn't filing a joint return. no
5. and he lived with us the whole year. yes
Step 2:
1. he is a US citizen
2. he is not married
3. my wife and i are not claimed on as dependent on anyone elses' return
Step 3:
1. he was not under age 17 at end of 2016