I think something nature related or something that symbolises freedom or rebellion in some way would be great -or even perhaps objects, foods, activities that brought hope/comfort/freedom to the character?
Bluebird is brilliant.
Some ideas:
[name_f]Lark[/name_f], [name_u]Sky[/name_u], [name_u]Lake[/name_u], [name_u]Ocean[/name_u], Wave, [name_u]Sunny[/name_u], [name_f]Rainbow[/name_f], [name_f]Cocoa[/name_f], Chamomile, [name_f]Poppy[/name_f], [name_f]Valley[/name_f], [name_f]Star[/name_f], [name_f]Bunny[/name_f], [name_u]Bird[/name_u], [name_u]Falcon[/name_u], [name_f]Tea[/name_f], [name_u]Teddy[/name_u], [name_f]Velvet[/name_f], Song, [name_u]Storm[/name_u], [name_f]Breeze[/name_f], Daffodils, [name_f]Snow[/name_f], [name_u]River[/name_u], [name_f]Melody[/name_f], [name_f]Honey[/name_f], [name_m]Baker[/name_m], Moonlight, [name_f]Sunshine[/name_f], Wildrose, Kestrel, [name_m]Forest[/name_m]
[name_f]Do[/name_f] these fictional sibsets sound plausible?
[name_f]Chloe[/name_f] and [name_u]Aiden[/name_u]
[name_f]Thessaly[/name_f], [name_f]Tamar[/name_f] and [name_m]Atticus[/name_m]
[name_f]Kaia[/name_f], [name_u]Cassidy[/name_u], [name_m]Kerrigan[/name_m] and [name_f]Cadence[/name_f]
[name_f]Leandra[/name_f] and [name_f]Alessia[/name_f]
[name_f]Amelie[/name_f] and [name_m]Raphael[/name_m]