Eavesdropping Only Leads to Sex
Prompt: Wincest: Dean drops off a dog that's missing its owner and Dean decides that Sam can take care of it for a few hours while Dean either finishes the hunt or tries to find the dog's owner, idc, but when he comes home the dog is licking Sam's cock/balls and Dean watches. Sam is super embarrassed when he realizes Dean can see him, but Dean is only really turned on. Maybe he urges the dog to mount Sam?