It is possible to claim your brother-in-law as a qualifying relative dependent, as long as he meets all five of the following conditions:
Relationship: The person must live in your home for the entire year (be a
"member of your household") OR
be related to you.
If you're filing jointly with your spouse and the person you want to
claim is a blood relative of your spouse, including half- and
step-relatives, foster and adopted relatives, then choose the
relationship to your spouse. For example, if you're claiming your
brother-in-law, who is your spouse's brother, enter that dependent as a
brother. Please see attached photo.
Gross Income: Generally, it must be less
than $4,050 (not including Social Security or welfare.)
Support: Generally, you must provide more
than half the person's support. Special rules apply for children of divorced or
separated parents or children receiving support from two or more people.
Marital status:
Generally, a dependent cannot file a joint tax return with a spouse. The only
exception is when the dependent files a joint return only to get a return of
taxes paid and, if separate returns filed, neither dependent or spouse would
have a tax liability.
Nationality: The person must be a United
States citizen; or a resident or national of the U.S., Canada or Mexico. An
adopted child that is not a US citizen or resident of the US, Canada, or Mexico
must live with you for the entire year.
Please see IRS link for more information. https://www.irs.gov/publications/p501/ar02.html#en_US_2016_publink1000220939
