Assuming your brother has a hold, he will be transferred to immigration detention. At that point, assuming he is not subject to mandatory detention, he can try to get bond and fight his case from the outside.
It is critically important that you get qualified and expert representation for the deportation/removal hearings. The Government will try to get the deportation issued. Neither the Immigration Judge, nor the Trial Attorney are there to help you. There are different forms of relief available which could result the granting of Lawful Permanent Residence. However, this requires large applications to be prepared and the necessity to prepare for trial. My firm has done this for several years, and if done properly, there is a very reasonable chance that it will be successful. If not done properly, the deportation order will be issued and your current way of living in the United States will end and you will either be on the run or be forcibly removed from the United States.