NigeriaorBust is correct... if current processing times don't change, you can expect your siblings to move to the US 12 - 13 years from the time you first applied. This is the time-frame for most of the world... certain countries have longer waits (as mentioned, the Philippines has the longest wait of 23 years).
There are lots of articles about what will happen over the next few years and there are good arguments both for the process speeding up or slowing down. Even if things speed up though, we're still talking about a multi-year wait.
