Responses

The duke is the oldest because the mother gave birth to the duke when the father of the current duke and his family is happy, and then the king love/(obsessed?) the mother of the current duke, the king became a threat to the happy family, they(the king) torture the father of the current duke, and the mother made a contract to the king to release the the father of the current duke, then they got (married?), and gave birth to the son of the king.
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So Duke: Oldest son
King: Second son. (=・ω・=)
why r ppl saying he has a twin? i tot there were only 2 brothers with different fathers