The Maloof family executed a "Purchase and Sale Agreement," a league statement said.
The deal is subject to the approval of the Board of Governors.
NBA.com said the Maloofs will be paid a reported $525 million for 65 percent of the team. Hansen has said he would try to buy the remaining 35 percent, which is held by minority stakeholders.
The new ownership would have a March 1 deadline to announce an intention to move the team and open play next season at a new location.
Hansen, the managing partner of Valiant Capital, a hedge fund company in San Francisco, has been buying land near Safeco Field, the home of the Seattle Mariners, as the site of a new basketball arena.
The Seattle SuperSonics, the most recent NBA franchise in Seattle, played at the KeyArena before moving to Oklahoma City before the 2008-09 season. The Sonics had been in Seattle since the franchise was granted in December 1966.
Seattle would be the fifth home for the Kings' franchise, which started in 1945 in New York as the Rochester Royals. The team moved to Cincinnati in 1957 and then to Kansas City, Mo., changing the nickname to the Kings, in 1972, and splitting home games for a time with Omaha.
The team was sold to investors in Sacramento in 1980 for $11 million and moved to California for the 1985-86 season.
The Kings haven't qualified for the playoffs since 2006 and are 16-25 this season.