For instance, Mosley lost to Canelo, but just say Mosley's son were to beat Canelo? (I know it's unlikely, but just an example ). What are some examples of this?
Obviously a very rare thing. The only one I can think of is Chavez Sr losing to Grover Wiley in his very last fight, and then Chavez Jr beating Wiley all of two years later.
Harold Johnson tried. Didn't really work out for him. Camacho Jr. "avenged" his father's earlier draw with Campas, although he performed as badly in that fight.