A 'Family Tree'report is also called a pedigree report. By definition, a family tree is an individual and that person's direct ancestors (parents, grandparents, g-grandparents, etc.)
You said, "I would like to print a complete family tree between two generations, eg all relations in these generations rather than the descendants or ancestors of one person."
??? Do you mean a report showing your marriage and your children, the marriages of your siblings and their children (that is two generations), and maybe your parents? (that is three generations.)
Try a Family Group report of yourself. That will show your data and the names of your parents, your wife's data and the names of her parents, your children's data andthe names of their spouses.
Try an Indented Descendant report. Start with the generation before the two generations you wish to show. If you want to show all the children and grandchildren of your parents, make your father the beginning of the indented descendant report.
If neither of those fit, please try to explain again what you want in your report.