Possibly. Since they lived with him for 12 months and he supported them, the only tests remaining is if they had less than $4,050 gross income and whether they are your "Qualifying Child". This basically amounts to if you yourself are required to file a return. See below. Please feel free to post any additional details or questions in the comment section.
The 4 tests that will qualify a relative as a dependent are:
- Qualifying Child: They are not the “qualifying child” of another taxpayer or your “qualifying child”.
- Gross Income: The dependent being claimed earns less than $4,050 in 2017 ($4,050 in 2016).
- Total Support: You provide more than half of the total support for the year.
- Member of Household or Relationship: The person (a friend, girlfriend, non-blood relative) must live with you all year as a member of your household.
A child isn't your qualifying relative if the child is your qualifying child or the qualifying child of any other taxpayer.
Child of person not required to file a return.
A child isn't the qualifying child of any other taxpayer and so may qualify as your qualifying relative if the child's parent (or other person for whom the child is defined as a qualifying child) isn't required to file an income tax return and either:
- Doesn't file an income tax return, or
- Files a return only to get a refund of income tax withheld or estimated tax paid.
What this means is if you are required to file a return, you are considered a taxpayer and must claim the child on your tax return.
IF you are not required to file his tax return (your income is too low to meet the requirement), and only files to get a refund, you are not considered a taxpayer, you don't have to claim the child, but he can (providing you meet other qualifications above).