If this is sensitive for your families, a workaround is necessary:
- Navigate to the family record.
- Pull out the blue "What Can I Do?" menu from the left.
- Select More Options.
- Click Update Family And Student Information.
- Enter the full name of Parent 1 into the Parent 1 First Name field.
- Enter the full name of Parent 2 in the Parent 1 Last Name field.
- Click Save Changes.
This is then how the names on the invoice will generate.
Keep in mind this will impact how you search for the family, if by name (ex. from Families > Manage Families) as the Parent 2 name will be located in the Last Name field.