Complex sentence: Her father, Sol Hammerman, worked for J.K. Industries in Chicago, a company founded by her grandfather, which he and his brother, Meyer Hammerman, turned it into one of the nation's largest children's clothing manufacturers at the time.
Split into simpler sentences: Her father, Sol Hammerman, worked for J.K. Industries in Chicago, a company that was founded by her grandfather. Sol and his brother, Meyer Hammerman, turned the company into one of the nation's largest children's clothing manufacturers at the time.