Jack Gustav's birth name is Gernot Gustav Fraydl.
Gustav Jonsson's birth name is Gustav Robert Jonsson.
Gustav Krupp von Bohlen und Halbach's birth name is Gustav von Bohlen und Halbach.
Tava's birth name is Gustav von Will.
You can learn all about him in wikipedia under his name.
Ernst Dittmer's birth name is Ernst Gustav Vilhelm Dittmer.
Gustav Gavrin's birth name is Gustav Schwarz.
Gustav Mahncke's birth name is Gustav Theodor Mahncke.
Gustav Leonhardt's birth name is Gustav Maria Leonhardt.
Gustav Sandgren's birth name is Gustav Emil Sandgren.
Gustav Esmann's birth name is Gustav Frederik Esmann.
Gustav Hintze's birth name is Gustav Hintze Holm.
Gustav Jonsson's birth name is Gustav Robert Jonsson.
Gustav Winckler's birth name is Gustav Frands Wilzeck Winckler.
Gustav Wiklund's birth name is Gustav Adolf Fingal Wiklund.
Gustav Knuth's birth name is Gustav Adolf Karl Friedrich Knuth.
Prins Gustav's birth name is Christian Frederik Vilhelm Valdemar Gustav.
Gustav Adolf Olsen's birth name is Olsen, Gustav Adolf.