Im 23 and want to adopt my brothers and sister as they are in foster care, is that possible and how long does it take

It is possible. From what CPS says, they make every attempt to keep the children with their family members. However I'll be honest, your age may be an issue. It won't stop you from adopting them, but despite what they'll tell you, it will make it hard... actually THEY (CPS) will make it hard.
Contact CPS, tell them your interest and get the process started. They'll have plenty of questions to ask you (can you support them, do you have a stable job and homelife, etc) You'll need to do a homestudy, most likely, and go through a few interviews. Depending on the state, and how much trouble they give you, I guess it may take anywhere from a few to 6 months at most?
You may ask if you can have temporary custody of them while you're going through the adoption process, but again its all up to them. GOOD LUCK!

Get a lawyer. You'll need one.