The word "unbrotherlike" signifies an act or behavior that is not appropriate for brothers or characterized by a lack of brotherly love. So, the antonyms for this term would be words that describe behaviors and actions that are kind, loving, and supportive. The antonyms for unbrotherlike could include words like caring, compassionate, brotherly, affectionate, friendly, amiable, congenial, warm-hearted, companionable, and affable. These antonyms emphasize the importance of having a close bond with one's siblings and treating them with kindness, respect, and understanding. They highlight the values of brotherhood and genuine love that can make relationships with siblings stronger and more fulfilling.