I know I already kind of made a post about this but all of your suggestions gave me ideas. (I’m really in to comping up with names so this is completely hypothetical)
Which do you prefer as a sister to [name_f]Fern[/name_f] [name_f]Elizabeth[/name_f] and [name_u]River[/name_u] [name_f]Jane[/name_f]
[name_u]Lux[/name_u] [name_f]Emilia[/name_f] or [name_f]Daisy[/name_f] [name_f]Katherine[/name_f]?
Definitely [name_f]Daisy[/name_f] [name_f]Katherine[/name_f]
Stylistically with the first [name_f]Daisy[/name_f] goes super sweet but [name_u]Lux[/name_u] has that spunkiness that goes really well with [name_f]Fern[/name_f] and [name_u]River[/name_u] that [name_f]Daisy[/name_f] doesn’t, I think I’m gonna go with [name_f]Daisy[/name_f] though!
[name_f]Daisy[/name_f] [name_f]Katherine[/name_f]
Daisy Katherine 1000%!!! How beautiful!!!
[name_f]Daisy[/name_f] [name_f]Katherine[/name_f]! [name_u]Lux[/name_u] [name_f]Emilia[/name_f] is beautiful, but I think [name_f]Daisy[/name_f] [name_f]Katherine[/name_f] matches [name_f]Fern[/name_f] and [name_u]River[/name_u] a little better
I definitely prefer [name_u]Lux[/name_u] [name_f]Emilia[/name_f] by a lot
daisy katherine! fits much better!
[name_u]Lux[/name_u] [name_f]Emilia[/name_f] 
i love it!!
Hmm… [name_f]Daisy[/name_f] with [name_f]Fern[/name_f] and [name_u]Lux[/name_u] with [name_u]River[/name_u]. Overall, I’d say [name_f]Daisy[/name_f].
They both go! I much prefer [name_u]Lux[/name_u] [name_f]Emilia[/name_f] 
[name_u]Lux[/name_u] [name_f]Emilia[/name_f], it balances the 1 syllable feel of [name_f]Fern[/name_f] with the unisex feel of [name_u]River[/name_u] and doesn’t tie you down so much to a word name/ nature theme
[name_f]Daisy[/name_f] [name_f]Katherine[/name_f] 100% such a gorgeous name!
daisy katherine!!!
I’ve never been a fan of [name_u]Lux[/name_u]. Maybe [name_f]Emilia[/name_f] [name_u]Lux[/name_u] if you had to use it. But for what you have [name_f]Daisy[/name_f] [name_f]Katherine[/name_f] gets my vote.
[name_f]Daisy[/name_f] [name_f]Katherine[/name_f]!
I prefer [name_f]Daisy[/name_f] [name_f]Katherine[/name_f].
[name_f]Imo[/name_f], [name_f]Daisy[/name_f] makes this sibset feel a touch unbalanced. Because [name_f]Daisy[/name_f] and [name_f]Fern[/name_f] are both girly, botanical names while [name_u]River[/name_u] is a unisex geographical name. That said, I do love the name [name_f]Daisy[/name_f].
I really like [name_u]Lux[/name_u] with this sibset. It adds a totally new element, while still fitting in well. It is not a nature name, but it is somewhat of a wordy name still. It has a very slight unisex feel to fit with [name_u]River[/name_u]. It’s a short, one syllable name like [name_f]Fern[/name_f]. It’s modern like [name_u]River[/name_u]. I think [name_u]River[/name_u], [name_f]Fern[/name_f] and [name_u]Lux[/name_u] are gorgeous.
If I could mix and match tho, I would choose [name_u]Lux[/name_u] [name_f]Katherine[/name_f]. I like that better then [name_f]Emilia[/name_f] so there are no repeating initials (Emilia and Elizabeth). And I think [name_f]Elizabeth[/name_f], [name_f]Jane[/name_f] and [name_f]Katherine[/name_f] are a better style fit then [name_f]Elizabeth[/name_f], [name_f]Jane[/name_f] and [name_f]Emilia[/name_f]. [name_f]Katherine[/name_f] makes the feel more extreme timeless classic.