Are dying people really seeing the souls of their dead relatives?

I heard when people are dying they call the names of some of their dead relatives or even hear them. Are they actually seeing them or are they hallucinating? When I read about the death of Louis XVII, son of Marie Antoinette and Louis XVI, it was said that as Louis XVII was dying at the age of 10, he said he heard music and the voice of his mother (who was already beheaded two years ago). I was pondering on this. Since Louis XVII was very sick and was dying there's a probability that he was only hallucinating, but could it be that he really heard his deceased mother's voice? Are dying people really seeing the souls of their dead relatives or at least hearing them?