Its really hard time for you and difficult to deal with your grief. I m very sorry for you going through this situation. I know its the serious problem for your father. I m really worried heard about your brother.
You have to take weight of your family on your shoulders after death of your father. Its your first responsibility. I think your father depressed from the tension of your younger brother. You should going to grief counseling group. This is the best way to deal with your all problems and grief. I hope its really helpful to you and also for your brother. You give console to your father.
Parents are responsible for children future but now he is in critical situation.
Now you need to be strong and give console to your family because you are older son of this family. Never loose your hope. I pray to God for you and for your family.
(((((((((((HUGS FOR YOU))))))))))