>>42351637
Murky and Protege's relationship is more brotherly than anything else. There's too much distance between them due to Protege's status as a slaver with Red Eye. That only breaks down at the very end of the story, after he renounces Filly (and his life's work) and leads the slave rebellion. Only then does Murky give him a hug.

It probably wasn't the author's intent, but Protege as written is the most lonely, unfulfilled character in Filly. At least P-21 got to fuck and cuddle a bunch of times.