As the Bible tells us to honor our father and mother are we suppose to honor our grandparents in too?

I love my mom and would do anything for her. I honor my mother. Her dad,my grandfather, I really don't care for because he is selfish, lazy and all he do is talk negative about other people. He talk negative to other people about his own kids, grand kids, sister, brother and friends. He got sick and had to spend some time in a nursing home for rehab and it seem like his focus was on who was coming to visit him instead of trying to get better. I don't care for him or care to have any kind of relationship with him. Since my grandmother died my mother been the one to take care of him. My mom does so much for him, such as seeing that he has three meals a day, wash and iron his clothes and making sure he takes his medicine, but he never says "thank you". He is an 80 year old man and he can't do anything for him self just like a small child. I know that how I feel about him is wrong. If he died tonight I wouldn't care. I want to do what is right in the eyes of the Lord, but how I when I feel this way?