The IRS provides a worksheet for determining support here.
If the 20-year-old is not a student, then they can be your qualifying relative if you provided more than half their support and they had gross income under $4,300.
For the student, there is no gross income requirement if she was a student for five months of the year and is under the age of 24. If that is the case, as long as she does not provide more than half her own support, you are eligible to claim her.
