hi faysal,
as wantmygcnow already mentioned, you can file a petition for your kids and children based on both your GC status and citizenship. however for your siblings and parents you can only file petition when u become a citizen.
now as for filing petition for your wife and kids, this is what my immigration attorney advised me: you can file a petition for your wife and kids when u are a permanent resident / GC holder (unmarried children only, doesn't matter if they are 21 or not). the waiting period starts then. it is longer when u r on ur green card then when u become a citizen. after you become a citizen whilst your initial petition based on ur GC status for ur wife and kids is still pending based, the process becomes faster and the time you have waited on ur previous petition counts in.
so lets say you are on ur GC now and u become a citizen in 1 year. lets also assume that (im not sure wot the time frames are) the waiting time for a petition for spouse based on GC status is 5 years and based on citizenship is 3 years. u file the petition now and the clock starts. in 1 year u become a citizen and at that time u have waited 1 year. if u were still on ur GC you would still need to wait another 4 years (5-1), but because u r a citizen at that time you will need to wait 2 years (3-1).
file ur petition as soon as you can. the waiting time will start then and will count when u become citizen.
hope this wasn't too confusing and it helped!
good luck!