It sounds like the dependency depends on if the son paid for over 50% of his own support or now.  You may want to look at the IRS worksheet to help you determine that:

https://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf

Once you find out if the son qualifies to be a dependent, post back here and we'll see what we can do.

Also, when talking to the mom, you may want to ask her if they are able to contribute to an IRA *IF* it would save them a bunch of money on their tax return.