How do you formally address wedding invitations to a family?

For a formal invitation to a family, the outer envelope should carry the parents' full names and titles, such as Mr and Mrs John Smith. If the parents are not married, use both names on separate lines, for example Mr John Smith and Ms Jane Doe. On the inner envelope, you can be slightly less formal. Write the family surname and then the children's first names, for example Mr and Mrs Smith and family, or simply John, Jane, Tom and Lily. If you are using only one envelope, put the parents' names on the first line and then the children's names on the following lines. This keeps the formality while making it clear that the whole family is invited. If the children are grown up and live away, it is better to send each one their own invitation. For a family where the parents have different surnames, address them separately on the outer envelope, each with their own title and full name. The inner envelope can then just use their first names and the children's first names.