When Thomson Corp. negotiated its $17 billion deal for Reuters Group PLC, Thomson Chairman David Thomson stayed on the sidelines through 18 months of talks, speaking to Reuters top management only on the day plans for the deal were announced in 2007.

For the scion of Canada's wealthiest family, the hands-off approach, described by people close to the merger, was par for the course. The family's formula over the past two generations at the media empire founded by Mr. Thomson's grandfather was 'surround yourself with business people