Before you say “I do,” you and your potential spouse need to decide if you want children. You might be able to disagree on the exact number of little munchkins you want running around as long as the numbers are close. It might not be a problem if he wants two kids and she wants three, but there may be no way to reconcile her desire for one child and his for a flock of seven.
The discussion revolving around children cannot simple end with “we both want kids.” You and your potential spouse also have to discuss how you would raise said hypothetical children. Would one of you quit their job? Would you put them in daycare or have family watch them? How big a part in the child’s life should religion play? How would you handle punishments when the child misbehaves?
You and your potential spouse should also discuss what to do if you both want kids but find out that one of you suffers from medical complications. When is a high risk pregnancy too risky? Are you open to fertility treatments? If so, what are you comfortable with undertaking? How much can you spend trying to subvert infertility? All of these questions need to be addressed.