This is best explained with an example. Amy Jones marries Mike Smith. They have two kids, Lisa Jones-Smith and Kyle Jones-Smith. So far, so good. A two-name last name is a bit long, but worth it for gender equality. But what happens when Lisa and Kyle grow up and want to marry people?
Let's imagine another family. Nora Johnson marries Ed Gibson. They have two kids, Ella Gibson-Johnson and Nate Gibson-Johnson.
The kids grow up and meet each other. Ella falls in love with Kyle. Coincidentally (to make our example easiest, without inventing more fake people), Nate falls in love with Lisa. What will their last names be?
The girls take the last name that originated with their mothers, and the boys take the last name that originated with their father, and they combine them. So we now have two couples, Ella and Kyle Johnson-Smith and Lisa and Nate Gibson-Jones. Easy!
- Although they are taking either their mother's or father's name with them when they get married, they still have a name-link to BOTH their parents (since their parents hyphenated their names).
- Although the brothers and sisters now have different last names than each other, this would be true if the traditional patriarchal naming structure was followed, as well, when the girls got married and changed to their new husband's name.
- In the above examples, the order of the last names was decided simply by the alphabet. Couples could default to that, or decide which sounds best.
- Gay and lesbian couples could decide which of their parents' names to take with them when they get married, or they could do a default alphabet scheme (for example, choosing the names that occur first and last in the alphabet, out of the four).
It's a plan that totally works! The only issue, of course, is that everybody, or at least most people, need to adopt it. Otherwise it falls apart. So consider it, people.