There are two type of dependents--qualifying child and qualifying relative (related or not related). In order to claim a non-related fiance and her son as qualifying relatives on your tax return, they would have to live with you the entire year and she must have taxable income of less than $4050. Here are the requirements:
1. The person cannot be your qualifying child or the qualifying child of any other taxpayer. A child is not the qualifying child of any other taxpayer if the child's parent (or any other person for whom the child is defined as a qualifying child) is not required to file an income tax return or files an income tax return only to get a refund on income tax withheld.
2. The person either (a) must be related to you or (b) must live with you all year as a member of your household.
3. The person's gross taxable income for the year must be less than $4,050 in 2016.
4. You must provide more than half of the person's total support for the year.
5. The person must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico.
If your fiance has income and is required to file a tax return, you cannot claim either of them on your tax return. If she has income but not enough to be required to file a tax return and only files it to get a refund of federal tax withheld, you may claim both her and her son as dependents if they meet the requirements listed above.
Claiming a child as a qualifying relative dependent does not allow you to claim qualifying child tax benefits which include Head of Household filing status, child tax credit, earned income credit and child and dependent care credit.
