Complex sentence: D'Adelswärd's grandfather had founded the steel industry in Longwy-Briey; which had become profitable enough to make Jacques d'Adelswärd a rich and' eligible' bachelor when he inherited at the age of 22.
Split into simpler sentences: D'Adelswärd's grandfather had founded the steel industry in Longwy-Briey. The family steel furnaces had become profitable enough to make Jacques d'Adelswärd a rich and' eligible' bachelor when he inherited at the age of 22.