Mori brothers split the family empire in 1999, then Minoru built Roppongi Hills

Taikichiro Mori, a former business professor, bought cheap land in bombed-out Tokyo after the war and built the real estate empire that made him the world's richest man in 1991 and 1992. His sons Minoru and Akira helped build it, but after his death in 1993 the brothers held conflicting visions: Minoru wanted bold urban re-engineering, Akira preferred conservative, short-term projects.

Rather than keep squabbling, the brothers parted ways in 1999. Minoru kept Mori Building with $1.3 billion in sales and 122 buildings under management; Akira took Mori Trust with $949 million in sales and 68 buildings. "A boat can't have two captains," Akira said.

Freed to pursue his vision, Minoru assembled more than 400 small lots over 14 years to build Roppongi Hills, a $2.25 billion, 27-acre mini-city with a 54-story tower and 793 apartments that opened in 2003, transforming a run-down district into Tokyo's most sought-after business address.

Each brother got a clean company in 1999; Minoru's $2.25 billion, 27-acre Roppongi Hills opened in 2003 and became Tokyo's most coveted business district.

The brothers' disagreement was about strategy, not money, so a split preserved both values.

Each brother got a focused portfolio and could invest at his own risk appetite.

Minoru's signature project needed a decade of patience only an owner could provide.

Splitting a family empire on strategy differences can beat forcing one captain; each half then moves at its own speed.

Mori Building continued to grow after the split, adding Ark Hills and the Shanghai World Financial Center, which opened in 2008 with the world's highest observation deck. Mori Trust also expanded steadily, and both companies survived Japan's two decades of stagnation.