Please explain more. Where are the parents? Do your parents work and have income? When you say "I take care of my siblings full time" are you referring to paying more than half of the expenses of the household including food, shelter, and clothing? No personal information, please, but we need details.
Yes I have parents but one is not in our life and my other lives with us and works but they work to half pay the rent while I pay the other half and we go even on utilities. I also help pay with rent and I buy the food and other necessities needed for them. So yes I mostly pay for everything besides rent which I still pitch in as well. @xmasbaby0
Your siblings cannot be claimed on more than one tax return. If your parent who works is filing a tax return and claiming the children (including you, actually) then they cannot be claimed on anyone else's return. If you are being claimed as a dependent on your parent's return, a dependent cannot have a dependent of their own.
It sounds like you are in a difficult situation and are doing all you can to make it better, which is really admirable.
Only the person who pays for more than half of the expenses--including rent, utilities, food, clothing, etc. etc.can claim the kids and file as Head of Household. If you add it all up----who is paying even just a little bit more---you or your parent?