If you need to change which spouse's record is set up as the Family Head for a particular family, you can accomplish this in the following manner:
Go to the Overview page for the client currently set up as the Family Head and click Clear Family in their Family section:
In our example, Albert E Einstein, Jr. is set up as the Family Head for this family, but we want to change Mileva M Einstein to our Family Head. After clicking the Clear Family button here, you'll receive a confirmation popup to OK the clearing of all family information associated with the contact. After clicking OK, the family information will be removed from the record and the former Family Head will no longer be set up as a Family Head.
You would then go to the record of the contact you want to establish as the Family Head and click Create New in their Family section:
You can then follow the instructions here for setting up your familial relationships and reestablishing this family setup.