Both brothers were angered by Haye's trash-talking before the Hamburg fight and Vitali, four years' Vladimir's senior at the age of 39 but still regarded as the superior fighter, said he wished the Briton had been knocked to the canvas.
"I was so happy (when) Vladimir won the fight but I was a little bit unhappy because I wished that Vladimir sent him to the floor," he told reporters.
"If I fought David Haye, I can promise one point. The reason why I would fight against him, just with one goal. To send him to the floor."
Vitali, unbeaten since he was stopped by Lennox Lewis eight years ago, said he was delighted that all the belts now belonged to the one family.
"We're very happy," he said. "And we're one team."
Vladimir also emphasized the family unity.
"We did spar in the past and we decided not to spar anymore because the competition is too strong. Neither of us wants to give up and we just decided to help each and not destroy each other," he said.
(Writing by John Mehaffey, editing by Justin Palmer)