Your boys have cute names and I like the subtle four letter theme maybe it would be fun for their sister to also have a four letter name 
The0, Jud3 and…
Nora
Lara
Lily
Rose
Evie
Enid
Maya
Iris
Ruby
Opal
Lola
Fern
Alba
Alma
Oona
Mara
Romy
Cora
Ella
Faye
Hebe
Mila
Wren
Lila
Nova
Ayla
Edie
Nola
Anya
Skye
Hope
Bess
Hope this helps