Ko'd a world champ and his brother - in consecutive fights!

I once made short work of a man on BoxRec's list of world champions...
... and in my next fight I ko'd his brother too.

Who am I?

 

It's a no to both Frazier and Nova - so maybe it's time for a clue:

The man we're looking for was himself a world champion... known more for his hitting-power than his technical skills!

 

Ok then:

Our man is on Ring Magazine's list of the 100 Greatest Punchers of All Time (from 2003).

 

When all hope seems lost, hh comes to the rescue

Yes, Stanley Ketchel it is. In February 1908 he needed less than a round to dispose of then reigning welterweight champion Mike (Twin) Sullivan... and 3 months later he ko'd his brother Jack in 20.