–Two (or Three?) Peas in a Pod
Usually, two names are not enough to set a letter pattern in stone, and your third baby is your big chance to branch out to a new letter. But in your case, I see two more factors to consider. First, your daughters' names don’t just have the same first initial; they share the same first three letters.
Mia, there has to be a story behind your George Washington benchmark. It made me laugh—and then it made me think, because the age of a name can be tricky to pin down.
–Hooked on Fox
It's a sad realization, isn't it? The first name you've been dreaming about for years suddenly bumps up against an immovable force: The surname. Some surnames are just more challenging than others to work with. And although Terry might seem innocuous, it can pose a problem because it resembles a first name (or nickname). So pairing it with a nontraditional first name—one that could also be a surname—is tricky.
Early on, I said we'd name the boys Silas and Elias and that was that. Then I got told by several people they were too similar. While they certainly are, I don't know if they rise to the level of "matchy" the way Iris and Lily or Holden and Hayden would—and they are named after their grandfathers! Am I wrong here? Should I pick new names? For the record, the grandfathers both approve.
I often hear from worried parents-to-be about matchy twin names. While sibling pairings are frequently a concern too, having twins seems to up the ante (and the stress level) even more. As in many of these cases, your pair is borderline: Some observers will call it way too much of a match, while others will see no issue at all.
–Need a Non-Binary Name
While many names bear the "unisex" designation (or reputation), few remain that way for long. There are occasional traditional names, like Morgan or Quinn, that have sustained usage by both genders over a fairly long period. So you could look to one of those, or a nickname used by both genders: Alex, Sam, or Chris, for example.
–Stuck in the Middle
I've fielded questions before from mothers and fathers with similar levels of anxiety over that second name on the birth certificate. But despite feeling stuck, Stuck, you're already on the right track here. As you've figured out, the middle spot offers a great opportunity to bring elements of contrast into a name—sharp consonants to balance liquid vowels, traditional names to dance with ultra-modern, or monosyllabic names to provide a break from long and winding ones.
–Seeking a Spelling Solution
Stick with the Sabrine spelling. Although the word "brine" rhymes with "fine," the association of Sabrine with the familiar name Sabrina should be strong enough to help most people pronounce the name the way you intend.
–Unsure on Surname
This is an unusual surname solution, but not an unprecedented one. Rather than expecting "trouble," expect some questions and confusion. The good news is, you have a ready answer to those queries: You want to keep a cherished family surname alive.
Yes, people may mistakenly assume that you are a blended family with kids from previous relationships. Close friends and even acquaintances can easily be set straight. And for one-time encounters, who cares?
Dad, I think we can put your fears to rest—especially if Eliot would be your son's middle name, not his surname. It’s a huge stretch to think that 8 or 10 years for now, some classmate will learn William’s middle name, consider that Billy is a traditional nickname for William, and then make a connection to an old movie (it came out in 2000) or Broadway musical (which debuted in 2005). After all, the Billy Elliot character is far, far removed from the Marvel or Star Wars universes.
Forgive me, Nana, but I am going to read between the lines of your question, because I'm seeing a powerful unspoken message here. You're asking me—the name expert—to validate your suspicion that this name isn't "real." Once you have that, you can object to it more politely (you didn’t say it; the Name Lady did!).