Can I Claim This Person as a Dependent?

Not according to IRS rules.

A dependent is someone else who depends on you for support.

However, you can usually claim one personal exemption for yourself, provided that another taxpayer is not entitled to claim you as a dependent.

For example, if your parent (or someone else) has claimed you as a dependent in prior years, it's a good idea to check with them before filing your tax return. 

No. The IRS doesn't let you claim your spouse as a dependent.

But don't worry. You're probably not missing out on a tax break.

When you file a return jointly, you and your spouse each receive an exemption from paying taxes on a portion of your income. The exemption is worth the same amount you would get for a dependent.

But what if my spouse and I use a filing status of married filing separately?

If you’re married filing separately, you can claim an exemption for your spouse if your spouse:

• Had no gross income
• Isn’t filing a return, and
• Wasn’t a dependent for another taxpayer, even if the other taxpayer doesn’t actually claim your spouse.

Certain relatives who qualify as your dependents don't necessarily need to live with you.

Here is a list of relatives who might qualify as your dependent, if they meet certain requirements (see below):

• Child, adopted child, step-child, eligible foster child (Special rules apply to children of divorced parents, though.)
• A descendent of any of the above 
• Mother, father, brother, sister, grandmother, grandfather, aunt, uncle, niece or nephew 
• Step-brother, step-sister, step-father, step-mother
• Any of these in-laws: son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law or sister-in-law

A relative must also:

• Be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico for part of the year; and
• Have no more than $3,800 gross income (except nontaxable Social Security benefits) in 2012; and
• Receive more than half his or her support from you; and
• Not be claimed as a dependent by another taxpayer or filing a joint tax return*

*You can claim an exemption for a person who files a joint return if that person and his or her spouse file the joint return only to claim a refund of income tax withheld or estimated tax paid.

Possibly. A person not your relative can be claimed as your dependent if they:

• Live in your home all year; and
• Have less than $3,800 gross income in 2012; and
• Receive more than half their annual support from you; and
• Are a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico for part of the year; and 
• Are not claimed as a dependent by another taxpayer.