However, his grandfather, Tadayoshi SHIMAZU, detected the brothers' characters and said, 'Yoshihisa is a person of virtue by nature, having the character to rule over three countries; Yoshihiro has martial vigor and outstanding powers of reason; Toshihisa is unrivalled in his ability to grasp the big picture of a situation, discerning the inherent advantages and disadvantages; and Iehisa is skilled at art of warfare,' showing the expectations he had for Yoshihisa.
しかし祖父の島津忠良は「義久は三州の総大将たるの材徳自ら備わり、義弘は雄武英略を以て傑出し、歳久は始終の利害を察するの智計並びなく、家久は軍法戦術に妙を得たり」と兄弟の個性を見抜いた評価を下しており、義久に期待していた。