The plan approved Wednesday by a 31-0 vote during a meeting in Irving, Texas, provided for transfer of the shares held by the brothers of chairman Dan Rooney II, the son of team president Dan Rooney.
The divestiture of gaming interests by all owners of the Steelers was consistent with league policy.
In a statement, the team said the agreement among the Rooney family calls for a closing to take place before March 31, 2009.
"We are looking forward to completing the remaining details of this transaction in early 2009," Art Rooney II said. "Today's vote ensures that the Rooney family will be associated with the Steelers and the NFL for a very long time."
Three new partners also were approved: James Haslam III of Knoxville, Tenn., Thomas Tull of Los Angeles, and the Paul family, based in Pittsburgh and Los Angeles.