You should be able to claim them (probably your GF also) as unrelated Qualifying Relative dependents because they lived with you the entire year and I assume that you provide the support since your GF does not have enough income to file . You would get the $4,050 exemption for each.
You cannot claim the Child Tax Credit, EIC or Child Care Credit because you are not actually related to them.
Here are all the requirements:
---Tests to be a Qualifying Relative (& Unrelated Persons)---
(Must meet ALL of these tests to be a dependent)
1. The person cannot be your qualifying child or the qualifying child of any other taxpayer.
2. The person either must be related to you, or must live with you all year (all 365 days - There are exceptions for temporary absences such as school, illness, business, vacation, military service) as a member of your household.
3. The person's gross income for the year must be less than $4,050 (tax-exempt income, such as certain social security benefits, is not included in gross income)
4. You must provide more than half of the person's total support** for the year.
5. The person is not filing a joint return.
In any case, the person must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico
The above is simplified; see IRS Publication 17, for full information.
https://www.irs.gov/publications/p17#en_US_2017_publink1000170933
** Worksheet for determining support
https://www.irs.gov/publications/p17#en_US_2017_publink1000171012
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
