Double Exposure or Spirit.

I have always been interested in spirit photography.
I have a photo taken in 1991 at the Xmas of that year.
It is a photo including my husband,two daughters,and grandchildren.
Now I say it is a double exposure but many people have observed other images within the photo.
On closer inspection,I can see one face that stands out and that is of my late mother in law.
I'm not very good at placing photos as a link,so if anyone can give me advice,I wll try to do this.
Don't hesitate to say if your opinion is that of a double exposure.
Petal