If your tree has a widow/widower and this marriage produced two children, and the spouse then remarried and the second marriage produced no children, how can you show on the family tree both spouses? If you put in the second spouse, although the first spouse remains in the info portion, she/he is eliminated appearing on the tree.
Since many people are widowed or divorced nowadays, this seems like something that should be able to be shown.
Currently, it is not possible to show two spouses at once in Family Tree Builder. You can always access the other spouse by clicking on the other spouse's name in that person's box.