Your older siblings can't be your dependents unless you provide more than half their financial support AND their taxable income for the year is less than $5050. This is called a "qualifying relative" dependent and should be eligible for a $500 "other dependent" credit but is not eligible for the $2000 child tax credit or the dependent care credit.
You can't be someone else's dependent and also claim dependents.
I don't know what credit you think you should get other than the $500 for each "other" dependent. You do not qualify for earned income credit, even if you claim your siblings as dependents, because you are not 25, and your siblings are the "wrong kind" of dependent to help you qualify for EIC.
