> If there are several individually wealthy family members it's probably more likely due to dilution.
While this is probably true in general, there are at least two famous exceptions from Germany.
There is the notable case of Adolf "Adi" Dassler, founder of Adidas, and his older brother Rudolf Dassler, founder of Puma, who separated from their joined shoe manfucaturing business and independently built two of the largest shoe (and now sports equipment) manufacturing companies in the world. Both still headquartered in the tiny 23000 people city Herzognaurach, Germany (close to Nuremberg).
And the similar story of Karl and Theo Albrecht, founders of Aldi (Albrecht Discount), which was split in Aldi Nord (north) and Aldi Süd (south), both growing their company in billion dollar businesses and each becoming billionaires. Granted though they had slightly different styles of running their business, their success was based on the same innovative business idea and a geographic non-compete agreement.