When Martok had discovered that Gothmara was involved in illicit experiments he had confronted her. She had rendered him unconscious, and while he was in that state she took advantage of him to conceive Morjod. As a child, Morjod was subjected to a number of enhancements by his mother, including those which would cause him to become a Hur'q at the appropriate time.
Shortly after Martok had become chancellor, Morjod and his mother staged a coup, destroying the Great Hall in the process and killing most of Martok's family and both of his half-sisters. Taking command of a Klingon vessel, Morjod showed his brutal tendencies by beheading the members of the crew that failed him in some way, and setting their heads under the viewscreen.
In a battle on Boreth, his father defeated Morjod in battle. When Morjod began turning into a Hur'q, Martok killed him before the transformation could be completed. Despite his earlier anger at Morjod over the deaths of his family, Martok held his son as he died, apologizing to the man and resolving to make things right. (DS9 - The Left Hand of Destiny novels: Book One, Book Two)