Here are some sibling names from various royal family trees : )
[name]Alexia[/name], [name]Pavlos[/name], [name]Theodora[/name]
[name]Victoria[/name] and [name]Madeleine[/name]
[name]Pilar[/name] and [name]Margarita[/name]
[name]Leonore[/name] and [name]Sofia[/name]
[name]Elena[/name] and [name]Felipe[/name]
[name]Beatrice[/name] and [name]Eugenie[/name]
[name]Etienne[/name] and [name]Isabelle[/name]
[name]Michele[/name] and [name]Catherine[/name]
[name]Yolande[/name] and [name]Louise[/name]
[name]Marie[/name]-[name]Zephirine[/name] and [name]Elisabeth[/name]-[name]Helene[/name]
[name]Nikolai[/name] and [name]Felix[/name]
[name]Christian[/name], [name]Vincent[/name], [name]Isabella[/name], and [name]Josephine[/name]
[name]Camilla[/name] and [name]Feodora[/name]
[name]Valdemar[/name] and [name]Marina[/name]
[name]Aliya[/name] and [name]Jalila[/name]
[name]Theodora[/name] and [name]Zoe[/name]
[name]Constance[/name] and Emeric
[name]Adelaide[/name] and [name]Salamon[/name]
[name]Magnus[/name] and [name]Thora[/name]
[name]Theresa[/name] And [name]Caroline[/name]
[name]Augustine[/name] and [name]Lucien[/name]
[name]Arthur[/name], [name]James[/name], and [name]Mary[/name]
[name]Ada[/name], [name]Maud[/name], and [name]Marjory[/name]
[name]Alice[/name] and [name]Pierre[/name]
[name]Gisela[/name] and [name]Pippin[/name]
[name]Victor[/name] and [name]Ferdinand[/name]
[name]Geoffrey[/name], [name]Alice[/name], and [name]Agatha[/name]
[name]Cosimo[/name], [name]Lorenzo[/name], and [name]Alessandro[/name]