The Mahon middleweight put a stop to Melvin Betancourt in the second round at the Agganis Arena and immediately turned his attention to securing a world title shot.
He said: “Andy Lee, he’s a good friend of mine but he’s got what I want in that world title and I’d knock my own brother out for the world title.”
Lee, the WBO middleweight champion, is currently recovering from a shoulder injury and it is unclear when he will return to the ring.
But O’Sullivan has another world champion in their sights should they miss out on the Lee fight.
WBC belt holder Miguel Cotto will face Daniel Geale early next month but ‘Spike’ could get a shot at him, providing he beats the Australian.
Ireland claimed one gold, two silver and five bronze medals at the World Women’s Youth and Junior and European Junior Men’s Championships in Taiwan and the Ukraine at the weekend.
Niamh Earley, Jason Harty, Natasha Logan, Jim O’Reilly, Lorcan Hurley, Kelsey Leonard, Anthony Johnston and Joanne Richards enjoyed success at both tournaments.
Light-welter Harty beat Poland’s Eryk Apresyan in Saturday’s 66kg final in Lviv, but Portlaoise light-heavy Jim O’Reilly lost to Arkadii Kartsan (Ukraine) in the 80kg decider.
Kildare’s Niamh Earley was beaten in the 52kg World Junior final by India’s Sandhu Mandeep on Saturday in Taiwan.