Your father is going to have a very difficult decision to make.
Your brother needs his own visa petition. Either a U.S. citizen sibling or his soon to be lawful permanent resident father will have to petition for him. Either way, and depending on the country he is in, it will likely take many years for him to join the rest of the family in the U.S.
You might want to have a consultation with an immigration attorney to see if humanitarian parole is a viable option for your brother
If you are eligible to apply for your father, you are also eligible to apply for your disabled brother. Depending on the details of your case, your father could file for your brother and then have the following options:
1. Also file a petition for your brother and apply for parole so your brother can live in the US to wait for his priority date to become current;
2. File for a reentry permit and go back to reside with your brother for two years without returning to the US;
Contact me if you want to do one or all of the above.