My opinion isn't a popular one on this. People always look at me like I'm crazy when I tell them I don't believe in ghosts, but I do believe people see something and that it is very real. I do believe there is a spirit realm, I just don't believe they are human spirits, because the Bible says that it is to man to be born once, die and then judgement. It doesn't say that man lingers around for 100 years and then judgement.
Let me start by saying that I grew up in a house where there was a ton of paranormal activity. It actually gives me the chills if I start to think about it.
Things were moved, my mom felt someone breathing on the back of her neck, I heard people calling my name, my dad actually saw an apparition, etc. We would leave and when we came home every planter in the house would be turned over. They were very heavy, so not possible the cat did it. Curtains being pulled aside by invisible hands as I left the house (my mom saw this), like something was watching me leave, etc. etc. etc.
I believe these things are real, but I'm not sure they are truly our loved ones or human for a variety of reasons. The Bible says not to talk to the spirits. I don't think we'd be warned not to do this if there wasn't a reason. After a lot of thought and experiences like those listed above, I think it is usually demonic activity at work. I won't say in all cases, because I just don't know, but I think in many.
I know that isn't something people want to hear, because they want to believe that apparition visiting is the loved one. However, I suspect it is true in most cases (maybe not all). I think if you are getting visits, you should test the spirits. Say something like, "In the name of Jesus, what is your real name?" You might be surprised at the answer.
Personally, I wouldn't invite it, just in case, but you might be braver than me. I'm sure I'll get lambasted for my opinion on this, but that is what it is.