Complex sentence: Unlike his sisters Stella, a fashion designer, and Mary, a photographer, James also has a much younger half sister, Beatrice Milly McCartney, born in 2003 to Paul and his second wife Heather Mills.
Split into simpler sentences: Unlike his sisters Stella, a fashion designer, and Mary, a photographer. James has a much younger half-sister, Beatrice Milly McCartney, born in 2003 to Paul and his second wife Heather Mills.