My parents have both gone on some years ago but I remember well in their golden years how things were. The most important thing is to love your parents and spend as much time with them as possible because you never know when they might not be around.
As we age we can become dependant on someone younger to help us. My mom was in a car accident that left her bedridden for some time. My dad was not able to care for her and she came to live with me.
Nurses would come in and work with her in therapy and the rest was up to me.She had developed some other problems and had to wear diapers and she needed to be waited on a lot. Over time she became more and more irritable and hard to deal with and I could not understand why. It was explained to me that she was feeling a role reversal and that she resented it.
Where once she cared for me and now the tables were turned and this mad her feel badly. She took to acting out and throwing dirty diapers against the walls and to hitting on me. I had no other choice but to put her in a nursing home.
She was mad at first but over time our relationship improved again, as there was no longer the role reversal taking place. Instead I would go and pick her up and take her out to lunch or to the park, things that we used to do together. It was a hard choice to make but I do feel I made the right one and I went to see her often plus she got to visit with people her own age and she felt much better about things. She passed away at the age of 94, happy.
Then my dad developed cancer and I made the offer for him to live with me but he said no he wanted to be with people his own age and wanted to go to a nursing home so that is where he went and every day I would go to be with him.
It is hard watching someone die with such a disease but you have to force yourself to be cheerful and act as normally as possible around them.
Bottom line and the point that I am trying to make is do your best, do what you feel is right and love them and act brave for their sakes.
Sometimes people with terminal illness will want to talk about death and will ask to do so. It may not be a subject that you are comfortable with but they have the need to express themselves so just listen and answer anything they may ask of you the best you can.