John Frederick III of Gotha died unmarried and heirless in 1565 and John William of Weimar tried to claim Saxe-Gotha , but the sons of the imprisoned John Frederick II entered their own claim . When John Frederick III of Gotha died unmarried and heirless in 1565 , John William of Weimar tried to claim succession to Saxe-Gotha , but the sons of the imprisoned John Frederick II entered their own claim .