No cancer patient is exactly alike but maybe this will help you.
My mother has Stage IV and it has gone to her lungs also. She is getting fluid in her lungs from the cancer. They put a Denver catheter in there to drain the fluid so that she will be able to breathe. It is very painful for her (they say its normally not painful, but for her it is excruciatingly so) when the catheters were installed (both lungs) and also painful when they drain the fluid. But if they didn't drain it, she wouldn't be able to breathe. It is like suffocating and not pleasant at all. She is on continuous morphine to help with the pain and is currently too weak to even take care of herself.
You can get a hospice nurse who will help you bathe, change diapers, clean dressings, empty fluids, etc and suggest you do so you are not completely stressed out yourself and able to enjoy your brother's company while you still have him here.