Arabellas little sisters name is....

[ASisterforArabella]

Arabella is going to be a big sister!

Any suggestions for names?

The one that popped into my head was Isadora but of the ones above I'd go for Iris being the strongest contender. Don't go matching initials unless you want a life of confusion and opening each others post

Oriana

Enid or Astrid

Caroline
Penelope
Beatrice

Jasmine
Rebecca
Emerald
Delphine
Louisa
Rosalind
Elspeth
Genevieve

Hester
Hannah
Hermione
Suzannah
Zinnia
Phoebe
Zoe

Clara
Rachel
Catherine
Beatrice

I agree with this sentiment and never cared a hoot about whether my own DCs names (5 of them!) “matched” or “flowed”, but I think OP probably means that given she and her partner obviously loved “Arabella”, what else are they likely to love as a name?
Possibly…

Aurora
Alexandra
Evangeline
Rose
Jasmine
Florence
Francesca
Theodora
Emma
Suzanne

Names need to "go" together, not to be matchy-matchy, but because you'll be yelling them together across the park for the next decade or so, and signing them on cards forever. So it is worth getting names that aren't difficult to say/yell one after the other (flow) and are not risible (or unfortunate for any other reason) when put together

Melissa
Melody
Melanie
Melisande

If you choose a name starting with A or possibly with any other vowel, you will get mixed up in the heat of the moment when you call to them to stop it, or just because you are too tired to think straight in the new baby phase.

Adelia

To make yelling at them easier, @AuntieStella ? 😀
I have 5 DC, and never yelled at them that much, though I did call them down for dinner, I suppose. I'm having trouble thinking of names that are difficult to call one after the other...

I was also a primary school teacher for many years, and had no problems with saying any names in succession. I did have 5 Lukes in my class once, though... that was a little tricky on occasion!

Of course I meant yelling in the sense of calling them over from some distance away, which is why I mentioned being in a park

This is a frequent occurrence if you have sporty, active DC.

(I had however temporarily forgotten how these days on MN you need to be much more precise than in ordinary conversation, so my apologies to anyone who read it as endorsing shouting at children in other contexts than getting their attention from a distance in public)

My first thought was Arianna but I think it's too close. Don't like them both starting with A.

Roseanna maybe

I think I would avoid anything too vowel-y or syllable-y. Eg ‘Arabella and Ophelia’ as a set just sounds too much of a mouthful and too flowery (imo!)

I like..

Grace
Charlotte
Kate
Eve
Rose
Zoe

We think we have landed on Sydney as a first name for our baby girl but are very much struggling for a middle name. I'd ideally like something long, feminine and possibly floral. Ending in a consonant would be a bonus for flow with last name. Thanks in advance for your help!

Emmeline
Eloise

Oh … also to add to Emmeline and Eloise… Eliza.

Martha
Jemima
Katherine (Kitty or Katie)
Eliza
Alice

Jacinta

Fenella
Felicity
Cordelia
Cecily
Clemency
Penelope
Patricia
Francesca
Saskia
Marianne

Rosalind
Susannah

Oh or Marguerite.

Sydney Raine.
I read it somewhere once and thought it was just so lovely

Our twin girl names were Arabella and Lilyana.. We had boys.

They got different names.