No info yet
Behind the Name has "Jesusa" as an entry -- fem firm of Jesús, like you thought -- so Jesusita is probably a diminutive of that. I also found a folk song that has Jesusita in the title, and a story of a 19th century woman named Jesusita in New Mexico.
I know a teenage girl named Campbell.
Matthias (or Mattias) came to mind right away -- not only is it three syllables but it's got the international and saintly vibe of your other kids' names. Benedict easily nicknames to Ben of course, but it also has the same feel. Maybe Augustine? Finding a three-syllable name without an obvious nickname is hard! Ooh -- maybe Cajetan? It's a heavy hitter but fits your criteria. Caspian? I love that one. Gabriel, Raphael, Phineas, Santino, Tobias ...
Micah was my first thought, and Matthias my second (though that's probably too New Testament?).
My sister has had Vivienne nn Vinnie on her list for a while, so that's my first suggestion. I think Genevieve, Evangeline, Evelyn could probably work too -- even though they don't have "vin" together, their prominent V's and N's lend themselves nicely to Vinny. Something like Verity Jean could work as well -- the V from Verity, the N from Jean.
I've just been perusing the abstracts from the conference -- there's quite a lot that has to do with Hungarian naming! I'm sure its location (Debrecen, Hungary) has something to do with it. This is the link to the abstracts, if you're interested: http://icos2017.unideb.hu/wp-content/uploads/2016/06/All-abstracts.pdf.
Would you be open to lengthening Eve to Evelyn or Evelina? I quite like how Fern sounds with both of those! Or Evette? Like "little Eve"? So sweet!
Oh this made me laugh! Thinking of possible explanations, I'm reminded of a family I know with three children who, when the children were teenagers, pseudo-adopted another teenager into their family and after a while dropped the qualifiers and simply referred to him as brother, son, etc. when speaking to others. If he continues being close to them so that, when the parents die, he's still considered to be a part of the family, I could see him being listed with the other children without explanation.
I'm so glad! I thought of Elise Geneva too, similar to Genevieve but has a nice flow.
To me, I find the stress on the final syllable of Elise followed by the stress on the first syllable of Catherine to be abrupt. A middle name with the stress on the second syllable sounds more pleasing I think. Elise Corinne is pretty; others include Elise Amelia, Elise Katrina, Elise Therese. Or, would you be interested in Elisa? Elisa Catherine has a pretty flow.
I love your lists, and I love Anna! Have you thought about Susanna? It can take all the Susie/Sukie nicknames, including sweet Zuzu, as well as all the Anna/Annie nicknames. St. Susanna's feast day is in August, which would be a nice bonus.
For your boy list, I had three ideas, all inspired by rhe length if your previous favorite Theodore: Thaddeus (nns Ted, Teddy, Tad, Taddy), Sebastian (nns Seb, Sebby, Bash, Baz), and Benedict (Ben, Benny, Beck, and I've seen Ned used for it too). All great saint names!
Choosing long or short will leave one of your girls out -- why not middling? Susanna's seven letters, Clara's five, it would be great to find a six-letter name you love. Verity and Violet work; I like Mariah for you too, as well as Honora, or a double name can feel like a good balance between short and long. Mary-Kate is two short names that feel like one long. Rosa-Jane, Pippa-Ruth, Nora-Tess, Eva-Grace -- so many fun and pretty options! (I was just using the hyphens for clarity, double names don't need them unless you want them.)
I love your girls' names! I love Felicity from your list -- I think it's the best fit; I also think Margaret's a great idea. Others that I'd suggest include Juliet, Lydia, Adelaide, Violet, Josephine, and Lucy.
I like the suggrstion of Rebecca -- I remember reading on here about a little Rebecca nn'd Ruby, love that idea!
I like it! Penelope's a sweet, fun name. It's #27 so maybe not as different as you'd like, but it has a lot of cute nickname possibilities to help distinguish your Penelope from others if needed.
I love Leo, and for his sister my favorite from your list is Nora. I could see Maura, Molly, and Clara fitting in well too. For boys, I love Henry with Leo. I'd also consider changing Milo to Miles, and my favorite Malcolm nickname is Mac, so I wouldn't consider Mal to be the default. I'd add Oliver to the list, and I wouldn't worry about popularity -- a good name's a good name, even if everyone else agrees. ;)
Perhaps Bennett, Simon, Royce, Roman, Sebastian (or just Bastian?), or Brooks?
Congratulations!! What bold, unusual names! I love the meaning behind each one. I'd love to know if you call them by nicknames, or are they always Daring, Taliesin, and St. Vincent?
Maybe Hendrix? Henning? Hyacinth? Hero? Hugh or Hugo?