Is Cordelia’s middle a family name? If not, I would choose something like Lavender–a good twinny similarity to [name_f]Sage[/name_f], without making the names “uneven”. I prefer to avoid that, especially with twins.
If [name_f]Sage[/name_f] IS a family name, I really like [name_f]Victoria[/name_f] with [name_f]Celeste[/name_f].