Is it normal to feel sad for your parents?

I’m 18 and my parents are over 50… As I see them get older, I see the change and I feel “sad” for them… It’s a bad feeling…. I feel sad myself because of that. We argue with my mom occasionally and I don’t really love her crazily. I’m better off alone, as an individual. But then again I can’t stop feeling sorry and sad for them… Is this normal? I feel like they are going to fade