Why do people get sick

So I realize that at 28 years old to still have grandparents is a big deal. Most of my friends and others I know do not have that honor of still having them around. The sad thing is my grandfather is dying. I saw him last week and he is holding on, but just barely. I feel selfish because I want him around to see me become a mother some day, but on the other hand I can only imagine what he is going through. He is in so much pain and I wonder what he is holding on for. Fear of dying, maybe, or more likely fear of leaving my grandmother alone. He is a wonderful man who helped me become a woman. Since I could remember he was always there for me. I would change his shows on tv when I was little to watch my own programs, and he never complained. He taught me how to tie my shoes, learn how to play cards, and most importantly he taught me how to be happy in my life even if things weren't perfect. He was a terrific influence on me, he showed me what a wonderful marriage can look like, the way him and my grandmother would just look at eachother. I swear if he was healthy enough they would still be getting down and dirty at 80 years old. Their love was uncondional and it was most noticed when I would come and visit and just watch them together. They way he would look at her walking away or the way he would talk to her. He had the best laugh. Even if you didn't know what the joke was his laugh would make you pee your pants, it was the most perfect funny laugh. If I close my eyes hard enough I can hear him laugh.

I'm done for now, the tears are falling and I can't really see the computer