The issue isn't how much he made. The IRS doesn't have an upper income limit for a person to be a "Qualifying Child." The issue is how much did he contribute to his own support (food, clothing, rent, etc).
For example, if his support cost $10,000 for the year, did he contribute more than $5,000 towards that?
Page 15 of this IRS Publication has a worksheet for determining support: https://www.irs.gov/pub/irs-pdf/p501.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
