Nothing is known about the youth of Vaišvilkas as he entered historical sources only in 1254 when he made a treaty, in the name of his father King Mindaugas, with Daniel of Halych-Volhynia.
Der vides intet om Vaišvilkas' ungdom, han optræder første gang i historiske kilder i 1254, hvor han undertegnede en traktat, på vegne af sin far, kong Mindaugas, med Daniel af Halych-Volhynia.