[name]Theodore[/name] [name]Caspian[/name], [name]Evelyn[/name] [name]Titania[/name], and [name]William[/name] [name]Rohan[/name] are fantastic! 
[name]Maeve[/name]- [name]Lovely[/name], but I’m not sure about it with your children’s names - to me, [name]Theodore[/name] and [name]Evelyn[/name] are more classic than [name]Maeve[/name]. The length isn’t a too big of a deal, though it might bother me a bit, personally. [name]Maeve[/name] [name]Arwen[/name] is a great combo, though.
[name]Stella[/name] - I think that [name]Stella[/name] works very well with [name]Theodore[/name] and [name]Evelyn[/name], but I’m not sure about the flow of a first name ending in A next to [name]Arwen[/name] as a middle, because the As cancel each other out - that might not be a big issue for you, though, if you take a longer pause before the two names…
[name]Jane[/name] - I like [name]Jane[/name] a lot, but it seems to lack the melody of [name]Theodore[/name] and [name]Evelyn[/name]. I like the flow of [name]Jane[/name] [name]Arwen[/name], though, and it sort of reminds me of [name]Jane[/name] [name]Austen[/name].
[name]Adeline[/name] - This is wonderful, too, and very nice with the names of your children. Like [name]Evelyn[/name], it ends with the N sound, but that doesn’t bother me in this case (I’m assuming that you say -line, rhyming with line, mine, nine, etc. rather than -lyn - correct me if I’m wrong). Normally, the repeating -N endings in a first and middle name combo might bother me, but I actually think that [name]Adeline[/name] [name]Arwen[/name] works - I love the alliteration.
[name]Louisa[/name] - I love [name]Louisa[/name] with your kids’ names and on its own! Nickname options include: [name]Isa[/name], [name]Lou[/name], [name]Lucy[/name], [name]Lula[/name], and [name]Lulu[/name]. Unless [name]Evelyn[/name] goes by her nickname, [name]Lenny[/name], all the time, the repeated L beginnings wouldn’t bother me as much. Then again, I’m not completely sold on [name]Louisa[/name] [name]Arwen[/name]… There’s the back-to-back A sounds, though that might be avoided - see [name]Stella[/name]. Also, there’s a slight W sound when I say [name]Louisa[/name] (loo-EEZ-uh/loo-WEEZ-uh), and I’m not 100% sure about the two W sounds in the combo.
[name]Elizabeth[/name] - [name]Elizabeth[/name] is the ultimate classic that’s never out of style, and I can see it with your kids’ names, easily. I love that it has an endless amount of nicknames, too! The E initial would probably bother me, though. [name]Elizabeth[/name] [name]Arwen[/name] has flows nicely, but it sounds a lot like [name]Elizabeth[/name] [name]Arden[/name]…
[name]Eleanor[/name] - Stylistically, this would be perfect with [name]Theodore[/name] and [name]Evelyn[/name], but I personally wouldn’t use matching initials for siblings. Also, [name]Eleanor[/name] could shorten to [name]Lena[/name], which is very similar to [name]Lenny[/name], so that might bother me.
[name]Susannah[/name] - Ditto to [name]Susannah[/name] - I love it and it’s great with your kids’ names, but I’m not sure about [name]Susannah[/name] [name]Arwen[/name], but it might work (sorry - see [name]Stella[/name] again)
[name]Anna[/name] - See [name]Jane[/name] - it’s lovely, but more simple (but that isn’t necessarily a bad thing) in comparison to [name]Theodore[/name] and [name]Evelyn[/name]. You can also use [name]Anna[/name] for a nickname for [name]Susannah[/name]…
[name]Beatrice[/name] - I love [name]Beatrice[/name]! [name]Beatrix[/name] is also one of my favorites, though [name]Beatrice[/name] is softer and more elegant. [name]Beatrice[/name] [name]Arwen[/name] sounds lovely, too.
[name]Imogen[/name] - [name]Imogen[/name] is nice, but there’s the repeated -en/-yn ending with [name]Evelyn[/name], and [name]Imogen[/name] [name]Arwen[/name] doesn’t have the best flow, in my opinion.
[name]Isolde[/name]/[name]Isolda[/name] - I prefer [name]Isolde[/name], but you would probably get less pronunciation issues with [name]Isolda[/name]. Pretty name, but I think that it’s mismatched with [name]Theodore[/name] and [name]Evelyn[/name] - sorry!
[name]Eloise[/name]/[name]Eloisa[/name] - I think that [name]Eloise[/name] works better with [name]Arwen[/name] and the sibling names, but I wouldn’t use it because of the matching E initial with [name]Evelyn[/name].
These are my favorites - the ones that work best with your kids’ name, flow best, etc.:
[name]Adeline[/name] [name]Arwen[/name]
[name]Beatrice[/name] [name]Arwen[/name]
Good luck!
