Can I and my sister claim our parents and our other two siblings as dependent at the same time or only one of us? We live in the same house for 6 months at end of 2017.

[basel-alnounou]

We all live together for 6 months at the end of this year 2017, I used to be the only one who works in the house until my sister started working recently. No one else beside us now works in the house, we pay the bills in half. Can I and my sister claim both our siblings and two parents as dependents or only one of us can?

[SweetieJean]

You said nobody else worked, but did anyone else have any income of any type?

[Opus 17 · Accepted solution]

 Each person may only be claimed as a dependent by one taxpayer, assuming that they qualify of course.  

 Also, only one of you can file as head of household.  To file as head of household, one of you must pay more than half of the household expenses, and claim at least one qualifying person as a dependent. The other one would file as single, and can claim some of the dependents however you decide to split them up.   If you pay exactly half of the household expenses each, then neither one of you can file using head of household.  I think it is unlikely that you pay exactly half, it only has to be $1  difference.  

[Hal_Al]

There are two types of dependents, "Qualifying Children"(QC) and standard ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income Credit and the Child Tax Credit. They are interrelated but the rules are different for each.
To claim your siblings, as QC, rather than standard dependents, these tests must be met:
1. He is under age 19, or under 24 if a full time student for at least 5 months of the year, or  is totally & permanently disabled
2. He did not provide more than 1/2 his own support (note how this is slightly different than the support test for a standard dependent
3. He lived with the relative (including temporary absences) for MORE than half the year (183+ nights)
4. He is younger than the relative (not applicable for a disabled child)
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child (this essentially means that you have the parent’s permission to claim the child, if the child also lived with the parent more than half the year)
6. If the parents of a child can claim the child as a qualifying child but no parent so claims the child, no one else can claim the child as a qualifying child unless that person's adjusted gross income (AGI) is higher than the highest AGI of any of the child's parents who can claim the child.