Lauren writes:

　　Our two little fellows, Rex, 3, and Leo, 18 months, will have a little sister later this year.

　　Our Hungarian last name is rather challenging to spell and difficult to pronounce, so we like the idea of keeping her name easy to read and say.

　　I like shorter, feminine, vintage names like Rose, Polly, and Milly, while my husband seems to lean towards more traditional names like Emily and Elizabeth.

　　We both love names that can transition easily to cute nicknames like Cece, Coco, and Milly, although this isn’t a must.

　　Whew! Hope this little girl isn’t as high maintenance as we’re making her name!

　　The Name Sage replies:

　　Leo and Rex are great names! They’re short on sounds, but long on style. And they both pair beautifully with a complicated last name.

　　I don’t believe a longer last name always requires a shorter first name. For every Ava Baumgartner, there’s an Isabella Krolikowski. But because you’ve given your sons shorter names, it seems logical to stick with something along the same lines for your daughter. Rex, Leo, and Anastasia could be siblings, but Rex, Leo, and Anya sound more like they’re members of the same family.

　　Of course, it’s very common to meet families where the boys’ names and girls’ names are very different in style, so there’s no reason to limit your list only to names with one or two syllables.

　　There’s a little bit of everything on my list of suggestions for Rex and Leo’s little sister.

　　Elizabeth – At four syllables, Elizabeth is a longer name. But it’s such an evergreen classic that it pairs beautifully with longer surnames. I noticed it was on your husband’s list, but I would have suggested it anyway, for two reasons. First, Elizabeth is regal, the name of one of history’s most famous queens. (As well as the current Queen of England.) Rex literally means king, and Leo is king of the jungle. Elizabeth rules, too. The second reason Elizabeth is on the list? Cute, sassy nicknames galore! Betsy, Libby, Liza, Lizzie, and Elsie all work. Milly might be a stretch, but I can imagine an Elizabeth answering to Billie or Lily, too.

　　Rose – After choosing a name from your husband’s favorites, I went back and looked at your list. I think Rose meets both of your criteria. It’s a classic, traditional name. But Rosie – or even Posy – makes a great short form. Rex, Leo, and Rose sound like quite the trio.

　　Cecilia – You have Cece on your nicknames list. There are lots of ways to get to the nickname Cece, including using the initials C.C., but one of the most obvious is Cecilia. It seems frillier than your favorites, but I think it fits. Another possibility that is less common, but closer to your husband’s suggestion of Emily? Cecily.

　　Mary – I know, Mary is too plain to consider, right? Except that it isn’t. Mary ranked Number 120 in 2014. Sadie, Samantha, Taylor, Ruby, and London were all more common than Mary. Because you have Polly and Milly on your list, I wonder if you’d like the idea of giving your daughter the name Mary and using a throwback nickname.

　　Coco – Would you ever consider Coco as a given name? It might feel a little too cutesy compared to Elizabeth and Rex. Longer names, like Caroline, Coralie, or Cordelia, might work better as a formal name, while Coco could be for daily use. It’s a bolder vintage pick than Polly, but one that stands up nicely to the strong sounds of Rex and Leo.

　　Willa – What would you think of Willa? It’s feminine, and feels more traditional. But fun nickname Billie is built-in, and I think you could easily use Milly for Willa, too.

　　June – June is as brief as Rose, but has the same ladylike vibe as Emily. But Junie is spunky and fresh – a great nickname!

　　Mila – I’ve saved my favorites for last. Mila leads to Milly. Like Rex and Leo, it’s a formal name that stands on its own. The only downside to Mila? It’s currently ranked in the US Top 100. And yet, Rex, Leo, and Mila are one of my favorite combinations – and I do think Mila makes a great compromise between your styles, especially with Milly as an option.

　　Esme – When I searched for sister names for Rex and Leo on Namehunter, Esme came up. It shares sounds like Emily, and has nickname choices like Mimi or May. Like Rex and Leo, Esme is a short, complete name that’s rich with style.

　　I’m not sure that I’ve helped narrow things down this time!

　　Two types of names stand out to me: first, I love the idea of Elizabeth called Betsy, Mary called Polly, or Caroline called Coco. All are classic, regal first names with spunky nicknames. It seems like that might please both you and your husband. Classic names work well with longer surnames, and give you plenty of options for short forms, too.

　　If Elizabeth and company aren’t for you, I think Esme might be a good compromise. It’s not as common as Emily, but has similar sounds. It shortens to Mimi or May, and Rex, Leo, and Esme sound great together!

　　Readers, what would you name a sister for Rex and Leo? And any advice for working with a more difficult surname?