I feel for you brother, It is truly hard to feel so helpless and watch loved ones endure difficult times. Sorrow is an inevitable part of human life, and something with which we all must deal at some point. As we get older, we generally get more in touch with our emotions, hence your father’s crying. But this is a good thing, as difficult as it can be to see. It is a healthy way for them to go through their grieving process. And you being there for them, listening, will help them more than you know.
Peace be with you.