Is Jack a real person that he knows? I have to admit that this concerns me a bit. Can you get a sense if these are ideas or thoughts or if he really thinks he "hears" this person talking to him. 4 year olds can be very imaginative and it is also very normal to want the opposite parent all to themselves, but there is something about what you describe that worries me a bit. I think you are right to be concerned and have your antennae up - but this could also be nothing significant. I would recommend having him evaluated by a quality child psychiatrist or psychologist - but only if you can find someone good who specializes in working with young children. Unfortunately, there are a lot of professionals out there that can overreact, overdiagnose, and overtreat. If you are interested in having him seen, what city/state do you live in? I may be able to suggest someone (I am a young child psychologist in New York).
I am wondering if he has heard possibly at school or day care/family some stories and he has in fact made up his own from what he has heard , children do hear bits and pieces from adults and don't always get the gist of what is being said .
This may sound weird and off the wall. But I strongly believe in paranormal stuff. Maybe he is seeing something u can't. My daughter used to talk to a lady in her room night after night. I finally did some digging and found out an older lady had passed away in the house about 50 yrs ago. I got the picture from the paper and showed my daughter. I asked her if she knew that lady. She said yes that who comes and talks to me at night. I never really believed in that stuff till that point. Like I said its a very far off idea but it couldn't hurt to look around and see if u can't find information on anybody with that name
He sounds very creative and imaginative.
It's not that odd for children to wish their same sex parent to be gone, especially at this age. They don't understand the true permanence of death, and frankly, would like to take on the role of partner to the opposite sex parent. "I'm going to grow up and marry Mommy" is something little boys say at this age - very innocently.
Interestingly, Disney caters to that. Can you think of a single Disney movie where the same sex parent of the main character is alive and functioning? Even ONE movie?