is it normal to feel guilty after someone passes?

I sure do. Two in one house passed within weeks of each other, both from undiagnosed brain metastasis of different cancer. I should have known they were sick but they always had pretended not to understand me for so long, I took their insanity as a personal insult. I thought they would tease me to the end. " No, I don't see nothing. No, you don't have a point..."