Family could be a major theme. Since it's about a son, his relationship with his parents, siblings might be explored. Another theme could be morality. As he is 'the good son', what does it mean to be good in the context of the story? Growth might also be a theme, like his personal growth as he faces different situations.
One possible theme could be family relationships. The good son's connection with his family members would play a significant role in the story. Another theme might be self - discovery. He could be on a journey to find out who he really is. Also, morality could be a theme, as he may face situations where he has to make moral choices.
One possible theme could be family. Since he is the son of a marquis house, family dynamics like loyalty, inheritance, and family pride would likely play a role. Another theme might be power, as being part of a marquis house involves political power and influence.
A third theme could be forgiveness. Maybe the son makes a mistake that hurts the mother, but through the story, they come to forgive each other and their relationship is strengthened.
One possible theme could be redemption. The bad son might realize his wrongdoings and strive to make amends.
One possible theme could be protection. The son using his fists to protect his mom from harm, whether it's physical danger or from unkind people.
Family bond. It emphasizes the strong connection between a mother and son. No matter how old they get, they are still there for each other, which is a very important aspect of family relationships.
A possible theme is the struggle against society's norms. In many cases, a gay son may face discrimination from society, and the father has to support him through this. Additionally, growth is a theme. Both the father and the son grow as individuals, the son in accepting himself fully and the father in becoming more understanding and empathetic.
One possible theme could be family. It's about the relationship between a mother and son which is a fundamental part of family.
One possible theme could be the struggle between light and darkness. Given Naruto's connection to Erebus (darkness), he would likely have to grapple with his dark heritage while still trying to uphold the values of the Hidden Leaf, which are more associated with light. Another theme could be identity. Naruto would constantly be trying to figure out who he is in relation to his father Erebus and his own ninja identity.
One possible theme could be coming - of - age. As the youngest son, he's likely to grow and develop throughout the story.