If someone (other than a qualifying child) who lives with me and is unemployed, can I claim he or she as a Dependent Relative?

Maybe. You might be able to claim the person as Qualifying Relative Dependent. To do so, all of these requirements must true:

• The person is your relative or your spouses (if married filing jointly) or has lived with you the entire year (365 days).
• The person’s gross income was less than $4,200.
• You paid more than half of the person’s support for the year.
• The person isn’t a qualifying child of any other taxpayer.
• The person isn’t filing a joint return, unless it’s only to claim a refund of taxes withheld or estimated taxes paid. Also, there would be no tax liability for either the person or the person’s spouse if filing separate returns.
• The person is one of these:
  • U.S. citizen
  • U.S. national
  • Resident of the United States, Canada, or Mexico
• You (or your spouse) can’t be claimed as a dependent.