There are several prerequisites for claiming family members as dependents. A dependant exemption is available for each eligible kid, which might include your child, stepchild, or foster child. A brother, a sister, a half brother, a half sister, a stepbrother, and a stepsister... they all qualify as children of your aunt or uncle who live with them... They can be claimed on Form W-4. The brother must be under the age of 19 and a student in high school or enrolled in an approved course of study (including college) at the time you file your tax return. The sister must be under the age of 24 and not a married woman. These rules may be changed by the IRS. You should consult the IRS website to find out what the current requirements are. Dependents cannot be claimed if doing so would cause you to exceed the maximum number of exemptions allowed for your filing status. For example, if you were only able to claim four exemptions this year, you could not claim five because that would mean you wouldn't have enough money withheld from your paycheck to cover your federal income tax liability. It's important to check with your tax advisor to make sure you're claiming all the allowances you're entitled to. This includes claiming any additional allowances for extended family members or other people you're responsible for helping with taxes.