The main plot of House of the Dragon centers around House Targaryen and their complicated family and political structure. For those familiar with Game of Thrones, House of the Dragon predates it by 190 years.
In episode one, the current ruler King Viserys I Targaryen suffers the tragic loss of his wife and firstborn son. Heartbroken and suffering from a degenerative disease, King Viserys is forced to make a swift political decision about who will be his successor. Will he choose his brother Daemon, a man who has shown countless acts of brutality during his time as commander of the City Watch, or will Viserys stray from the beaten path and choose his daughter Rhaenyra Targaryen? She would be the first female to rule the Seven Kingdoms.
The topic of the transfer of power to the next generation can be complex if a family hasn't had proper succession planning. Like many before him, King Viserys must navigate through his emotions and ultimately pick the successor who will be the best fit for his kingdom.