I’ve got cousins called [name_m]Calvin[/name_m] and [name_u]Jasper[/name_u] Those names are grand!!
From your lists, I love [name_u]Florence[/name_u] (and [name_f]Annelise[/name_f] in second place) for a sister and [name_m]Soren[/name_m] for a brother. They feel cohesive and playful all together without many sounds repeating, making each distinct.
[name_u]Adrian[/name_u] and [name_f]Dorothy[/name_f]!
[name_m]Soren[/name_m] works as well, but I prefer [name_u]Adrian[/name_u]. [name_m]Baxter[/name_m] shares many sounds with [name_u]Jasper[/name_u].
[name_f]Genevieve[/name_f], [name_u]Florence[/name_u], and [name_f]Annelise[/name_f] are great choices as well – I just like the more homespun feel of [name_f]Dorothy[/name_f] with [name_m]Calvin[/name_m] and [name_u]Jasper[/name_u]. [name_f]Soleil[/name_f] and [name_f]Serena[/name_f] are pretty, but do feel like a bit of different style to the others.