Maynard Plumm is the younger brother of Lord Ossifer Plumm. He was crippled from a fall during his childhood.
As children, Maynard and his brother, Ossifer, visited the Rock. Tyrius Lannister jested with Maynard and told him that the ancestral blade of House Lannister, Brightroar, was kept at the highest point of the Rock, atop one of the balconies of the ringfort that could only be reached by climbing. Maynard believed him and crippled himself attempting to climb to the balcony.
Ossifer Plumm, brother