A US citizen over the age of 21 can petition for siblings. But it won't be until about 12 years later until they can apply for permanent resident status. If they have been in the US without status they will have a significant problem getting a green card for that reason. You (and your siblings) should meet with a qualified immigration lawyer in order to get a full explanation of how the system works, so that you can make informed decisions.
There is a visa category of brothers and sisters of US citizens. As such, if you become a US citizen you can file for all of your brothers and sisters, regardless of where they live.