No, I don't think they do. I think it's just a comforting myth people are told to help them through the grieving process. There's nothing wrong with this. If it gives peace to others, far be it from me to disabuse them of their belief. After my youngest brother died some years ago, I went through a period when I gave this idea serious consideration. I reached the conclusion I reached for reasons I won't go into here, mainly because I don't want to upset anyone who may have recently lost a loved one. I'll just say that I sure hope none of my dead family or friends are watching over me. I hope they have better things to do in whatever afterlife there may be than wasting their time watching me.