We have our boys names decided and have had them decided for some time now [name]Rocco[/name] and [name]Roman[/name]. They seem matched enough for me and have a similar vibe. They have the same initial sound but are distinct enough names for twins. If only the girls could have been that easy. Right now we both really like [name]Calliope[/name]. My husband has recently mentioned that he really likes [name]Cassandra[/name] as a possible name. He is also quite fond of [name]Elliot[/name] on a girl and I kind of like the idea since I have a very unisex name as well. We are still considering [name]Aurora[/name], [name]Amaya[/name], and [name]Cambria[/name] but I just don’t know if they are right. We have given up on [name]Jordana[/name] because we just cannot find anything we like to pair it with. What would you suggest for us? If you could name our twins based on our style what would you name them?
[name]Calliope[/name] and [name]Cassandra[/name] are both mythology; I think they match nicely. Some other mythology-type names:
[name]Ariadne[/name]
[name]Artemis[/name]
Adrasteia / Adastreia
Alecto
[name]Cassiopeia[/name]
[name]Callisto[/name] / [name]Calisto[/name] / [name]Callista[/name]
I really like the B/B and B/G combos you’ve chosen! I put those 4 names in at nymbler.com to get some more girl ideas you might like, and it came up with [name]Veronica[/name], [name]Valentina[/name], [name]Antonia[/name], [name]Vivian[/name], [name]Camilla[/name], [name]Ariadne[/name], [name]Cecilia[/name], [name]Serafina[/name], [name]Marcella[/name], [name]Scarlett[/name], [name]Aurora[/name], [name]Chiara[/name], [name]Serena[/name], [name]Aurelia[/name], and a bunch more… Any of these sound good to you?? If you wanted a unisex pair, what about [name]Elliot[/name] and [name]Emery[/name] ([name]Ellie[/name] and [name]Emme[/name])? I do like how [name]Calliope[/name] and [name]Cassandra[/name] sound together, but if they go by [name]Callie[/name] and [name]Cassie[/name] it might sound a bit too similar… I don’t think it’s so bad though, but something to consider…
I also noticed your due date, what a cool birthday that would be!! 
I love [name]Amaya[/name], but if you like a name-set like your boys names…[name]Calliope[/name] and [name]Cambria[/name] are gorgeous.
[name]Love[/name] [name]Rocco[/name] and [name]Roman[/name] together! I also [name]LOVE[/name] [name]Calliope[/name] and [name]Cassandra[/name] together – similar with the two Cs and also similar in origin. So perfect. Given your choice for the boys’ names, those seem like the perfect girls’ set for you.
That being said … I have never been of the opinion that twins’ names HAVE to match (I think that’s a minority on this site), so if you wanted to go with [name]Calliope[/name] and [name]Elliot[/name], I think that would be fine and now that I see them written down, they do kind of match. But, similar to what pp said about [name]Calliope[/name] and [name]Cassandra[/name] – if their nns are [name]Callie[/name] and [name]Ellie[/name], that could get confusing (even more so than [name]Callie[/name] and [name]Cassie[/name]).
I don’t like [name]Calliope[/name] because of the pronunciation – cal-ee-oh-pee – but I love [name]Cassandra[/name]!
I would do [name]Cassandra[/name] and [name]Callista[/name] or [name]Cassandra[/name] and [name]Calypso[/name]. They are both names from Greek mythology and they both have the same sort of sounds but aren’t too similar.
I love Danteas idea of [name]Callista[/name] and [name]Cassandra[/name], or [name]Cassandra[/name] and [name]Calypso[/name].
Also, [name]Cassandra[/name] and [name]Sibyl[/name] may be up your alley. [name]Cassandra[/name] means prophetess and [name]Sibyl[/name] means Seer. Could be a nod towards your happy futures together. 
Oh wow a lot of those are nice! Thank you! I do like [name]Serafina[/name], [name]Scarlett[/name], [name]Aurora[/name], and [name]Chiara[/name]. [name]Emery[/name] is ok I think I would like [name]Emerson[/name] more but still nice. I hope I make it to the due date, I would love for them to have that birthday.
I say [name]Calliope[/name] as cal-EYE-oh-pee and I have never heard anything else so that is the pronunciation I would use for her. [name]Callista[/name] is nice too. [name]Calypso[/name] seems like maybe a little too much but I don’t know.
[name]LOVE[/name] [name]Calliope[/name], [name]Elliot[/name], and [name]Aurora[/name]!!! I love your names
[name]Do[/name] you want them to have the same initials? [name]How[/name] about something like [name]Calliope[/name] and [name]Charlize[/name]? Other ideas:
[name]Pheobe[/name] and [name]Penelope[/name]
[name]Aurora[/name] and [name]Belle[/name] - Not the same initials, but both a Disney princess
[name]Rory[/name] and [name]Rosalie[/name]
[name]Georgia[/name] and [name]Grace[/name]
[name]Heidi[/name] and [name]Haven[/name]
[name]Maia[/name] and [name]Maeve[/name]
[name]Lila[/name] and [name]Lucia[/name]
I want the names to have some sort of connection, it can be meaning, initial, or anything really as long as it is a connection of some sort.
I love the suggestion of [name]Cassandra[/name] and [name]Sibyl[/name], since they have similar meanings.
Have you heard of/considered the name [name]Amarantha[/name]? It’s a bit of a mouthful, but could easily be shortened to several nicknames - I really like it paired with [name]Aurora[/name], since it means “unfading” - together they’d be “unfading dawn”, which I think is gorgeous!
What do you think of these combos?
[name]Chiara[/name] and [name]Lucida[/name]/Lucia/Luciana - both mean clear
[name]Aurora[/name] and [name]Roxana[/name] - both mean dawn ([name]Rory[/name] and [name]Roxy[/name] would be so cute!!)
[name]Serafina[/name] and [name]Scarlett[/name] - means fiery and red, respectively… and they sound great together
I like [name]Serafina[/name]/[name]Seraphina[/name] and [name]Scarlett[/name] that could be a really cute sibset
I just wanted to say that I [name]LOVE[/name] that idea… [name]Amarantha[/name] and [name]Aurora[/name] sound amazing together!
I have always loved [name]Cassandra[/name] with [name]Anastasia[/name]. They both have a similar feel to me yet are very distinct names. They could have similar NNs to if you wanted; [name]Cassie[/name] and [name]Annie[/name], [name]Stacy[/name] and [name]Sandra[/name], [name]Sandra[/name] and [name]Stasia[/name], [name]Sandy[/name] and [name]Annie[/name] to connect the names.