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I agree that Paul and Peter together sounds more biblical than either name does on its own, or than other pairings of names from the bible. Even something like Ethan and Caleb - names that I individually associate more with the bible - doesn't have the same impact. I wouldn't necessarily expect Ethan and Caleb's parents to be religious, but Paul and Peter sound like a pair of altar boys.
Robbing Peter to pay Paul came to mind immediately.
There's the Modeste/Modesta/Modesto/Modestus family of names. You could try a new ending to make it more neutral (although Modeste could work as is), like Modestin or Modestux or Modestal.
Or Maristella could become Maristellan (Mari/Mary is feminine, Stellan is masculine). That gives you the M and the ist.
Monserrate (mountains are gender neutral!)
Madalitso (appears to be used on both men and women)
Only if he has a twin brother Rover.
Fido is absolutely 100% dog. Not that I've ever met a dog named Fido, but that's beside the point. Culturally (I'm in the northeast US), Fido is a dog name and not by any stretch of the imagination suitable for a person.
Man, you're tough. :D
I like Milo best.
But, on the more general concern, I think it's much better to give a baby a "big" name to grow into than to give a future adult a twee, cutesy name to grow out of. Please don't let that hesitation hold you back from a great name! Your child will spend many more years as an adult than a small child, after all.
How about Adriana, Anna (I love the nicknames Nina and Annika for this), Adeline, Adelaide (I guess I'm all about the A names at the moment), Caitlin, Brianna, Molly (I prefer it as a nickname for Mary or Miriam, but those seem less your style), Isobel, Eliana, or Ella?
I would suggest Jack if John names weren't out. Elijah, Ethan, Owen, Mac (short for any of the Max- names, Malcolm, Malachi, maybe Michael??), Matthew, Aaron, Samuel, Alexander, or Zachary?
Have you tried the Name Matchmaker on this site? My search using it suggests Hector, Cyrus, Adrian, Roman, and more -o endings than I knew existed. :)
In rank order, I prefer:
-Alexandra: classic, regal, very familiar and well-liked yet pretty uncommon at a rank of 120 last year
-Charlotte: a perfectly nice name that I just don't really like, maybe in part because I do love Caroline (both are variants of the same thing)
-Emma: fine but so "meh", this name just feels as bland as dishwater to me
-Hailey: this one is really insubstanatial; Gabriel and Olivia are current and trendy but also traditional, while Hailey lacks this last element (and is trending towards feeling dated besides)
-Henry: so handsome!
-William: a great name but boring just because it has been so common for so long
-Cass: too nicknamey but the idea has potential - Caspar, Casimir, Cassander (maybe all a little too rare for you?)
Gabriel, Olivia, and...
Maxwell, Nathan, Dominic, Noah, Julian, Isaac
Abigail, Claire, Hannah, Madeline, Audrey, Lucy
I don't think BJ will be an issue, but I like Ethan a lot better than Bryce.
Louise/a goes great with Edith. June, Ruth, Maeve, Willa, Opal, and Harriet also come to mind (without checking previous suggestions).
I agree with everyone who thinks you should look for another family name for the middle (or at least something with personal significance / a story). I think it's best to be consistent amongst siblings with this sort of thing, as much as possible.
A test to try: if you call "Josephine!" across the house, does Genevieve come running? I would think they might twist together into Genephine and Josevieve. They're just slightly too similar for me (initial J sound, 3 syllables with the same stress pattern, long E in final syllable).
Default nicknames are easier to avoid than they used to be. The idea of a Christopher not being called Chris was pretty much unthinkable in the '80s, but is completely doable today. A few people may call her Josie, but "Oh, we call her Josephine" (or Peppa or Jojo) should set that straight most of the time. Other possible nicknames are Posey, Joss, or Fina.
I strongly prefer Vivienne.
As others have said, I am super skeptical of that etymology for Tiegan, and whether it is truly a traditional name.
I'd rather be alive/full of life than a lost princess anyway. ;)
How did I not think of Elizabeth???
Your suggestion of Charlotte reminds me of Caroline, which is a favorite of mine and goes really well with the siblings.
I don't love either of them, but I think they're perfectly fine and work well in a US context.
Congratulations, how exciting!
I'm shocked Stellan is so low on the charts! Without checking popularity, here are a couple ideas: Lucius, Hugo, Dashiell, Asher, Magnus, Caspar, Daphne, Linnea, Phoebe, Ingrid, Freya, Astrid.
I love your children's names.
Boy suggestions are easy - Christopher, Thomas, Edward, Peter, Matthew, James, Charles, Zachary. Girls a little trickier, as the super classic names tend to have a little bit older/mustier vibe than the ones you have chosen so far (e.g. Mary, Helen, Ruth). How about Lucy, Rachel, or Catherine?
Another resounding vote for Catherine "Cate."
I very much agree that a clearly feminine name is better with the masculine surname.
My favorite is Madeline, followed by Sophie and Hazel.
I love the idea of Cordelia... or Cornelia if you really want to go fusty!
Rosalie and Coralie are a bit much together, although I can definitely see why they would appeal to the same people. For me, it's -ed nicknames for boys. "This is my son Freddie and his brother Teddy. Over there are my other sons, Ned and Jed." :D