To go with [name_f]Aurora[/name_f] [name_f]Maeve[/name_f] ([name_u]Rory[/name_u]) and [name_f]Matilda[/name_f] [name_u]Valentine[/name_u] ([name_f]Tilly[/name_f]).
[name_f]Elowen[/name_f] [name_f]Sylvie[/name_f] ([name_f]Lola[/name_f]/[name_f]Winnie[/name_f]) - [name_f]Elowen[/name_f] and [name_f]Aurora[/name_f] have flowy, soft, open-mouthed sounds. Together they make [name_f]Matilda[/name_f] sound a bit clunky.
[name_f]Imogen[/name_f] [name_f]Saoirse[/name_f] ([name_f]Gigi[/name_f]) - lacking some of the wonderful romance of [name_f]Aurora[/name_f] and [name_f]Matilda[/name_f].
[name_f]Delphine[/name_f] [name_f]Sorcha[/name_f] ([name_f]Delphi[/name_f]) - perfect!
[name_f]Oona[/name_f] [name_f]Jacoba[/name_f] (no nickname unfortunately) - [name_f]Oona[/name_f] has a lot going for it, but it might be too bold. [name_f]Jacoba[/name_f] is an amazing name (again, quite bold).
[name_f]Sylvie[/name_f] [name_f]Ondine[/name_f] ([name_f]Vivi[/name_f]) - [name_f]Ondine[/name_f] is simply stunning and would work as a first, too.
I think [name_f]Sylvie[/name_f] [name_f]Ondine[/name_f] and [name_f]Delphine[/name_f] [name_f]Sorcha[/name_f] work best. [name_f]Oona[/name_f] will work but not as well, especially when it’s a lot stronger than the pet names [name_u]Rory[/name_u] and [name_f]Tilly[/name_f]. ([name_m]Just[/name_m] to answer your question, my favourite firsts are [name_f]Delphine[/name_f], [name_f]Elowen[/name_f], and [name_f]Imogen[/name_f], and my favourite middle is [name_f]Jacoba[/name_f] because it’s so stylish and unique).
But, I’ve given this quite a bit of thought, lol, so let me tell you about [name_f]Ondine[/name_f]'s potential as a first name in your sibset. As I was thinking of [name_f]Sylvie[/name_f] for a first, I couldn’t help staring at [name_f]Ondine[/name_f] until it began to outshine [name_f]Sylvie[/name_f]. I was also thinking that [name_f]Sylvie[/name_f] would be perfect as a middle because then you’d have a ‘v’ in each of their middle names!
[name_f]Ondine[/name_f] has the n/ee/een endings you seem to be favouring in your options this time around.
It has a flow that’s almost as smooth [name_f]Aurora[/name_f], except that it’s interrupted by a ‘d’ like [name_f]Matilda[/name_f]. So [name_f]Ondine[/name_f] creates a balance across the sibset, phonetically. For the same reasons, I think [name_f]Delphine[/name_f] and [name_f]Francine[/name_f], too, are lovely potential firsts.
Other thoughts. If you like [name_u]Tristan[/name_u] for a boy, why not [name_f]Tristana[/name_f] for a girl? I have it high on my list, and plan on using either [name_f]Tawny[/name_f] or [name_f]Tasha[/name_f] (taw-sha) as nicknames. You could even do [name_f]Ani[/name_f]. There is also the beautiful shortform of Stana.
My other suggestion is [name_f]Faye[/name_f]. I was thinking it would be nice to have a one-syllable name that has a long sound in your sibset. Because of the drawl in [name_f]Faye[/name_f], it has some weight to it, even though it’s appears soft, and would therefore hold its own in a sibset with two three-syllable names that have lightness to them.