When I imagine finding myseslf in hell or the realm of hungry spirits after death, I wonder if I would even think much about those I had left behind. I might even resent and envy them, still in this world, which, horrible as it is, is a walk in the park compared to the hunger realms or hell.
If I found myself in heaven, where there is only pleasure and no suffering, I wonder if I would even care about them. If I did, I would feel deep satisfaction, because that would be proof that the causes I made in the past had made it possible for me to feel compassion for others even when I myself am not suffering. That would be proof, in my mind, that I had cultivated bodhisattva consciousness during the life I had just left, and could hope to transcend even heaven in the future and reach enlightenment.
When the spirit (life force) leaves the body, it moves on in accordance with the causes made in the past.
It seems to me that a spirit who stays in this world, manifest as the person he/she once was does so by cause. There must be some sense of frustration, something left undone that must be finished before they can leave this world behind. Or maybe it's an attachment to the body left behind, or attachment to loved one in this world. I don't think we common mortals have the wisdom to know anyone's path through past, present and future.
What I do believe as a Buddhist is that living beings are never born, never die, we just change form in accordance with causes and conditions. I have never seen a ghost appear to me looking exactly as somone did while alive, but I have got feelings during sitting practice, especially when I think of my parents, that have gradually increased my conviction that we can commune with those who have lived and died in this world. I believe not only that our thoughts reach them and help or harm them, but also that their thoughts reach us as well, and that we can learn from them to our mutual benefit.