I had a chat with my dad's brother, my uncle one night, and he eventually got everything off his chest!! (not a great night to day the least)
He expressed the guilt that he hadn't been able to do more for his brother, he resented that alcohol had taken his life, the fact my dad in his opinion, didn't care enough about him and the rest of the family to stop drinking, he was talking from a normal drinker stance, we know different, but he was frustrated!!
. . . and here I was, his brother's flesh and blood, beating alcoholism and becoming Sober, showing it can be done, and everyday reminding him what my dad's alcohol addiction did, it took away his brother!!
Maybe your Grandfather is constantly reminded of his daughter through you in the same way!!