|Allegiance|| House Peake|
|Born||At the Reach|
|Book(s)||The World of Ice and Fire (mentioned)|
Ser Mervyn was standing guard at the door to Queen Jaehaera Targaryen's chambers on the occurrence of her death. Mervyn killed his own sworn brother, Ser Marston Waters, during the turmoil of the regency after Marston tried to have Mervyn arrested.