Complex sentence: Later, along with his younger brothers, their South Island estates stretched from Banks Peninsula to Otago with similar holdings in the Hawkes Bay-East Coast regions they together controlled, by the 1850s, in excess of 300,000 acres.
Split into simpler sentences: Later, along with his younger brothers, their South Island estates stretched from Banks Peninsula to Otago. With similar holdings in the Hawkes Bay-East Coast regions they together controlled, by the 1850s, in excess of 300,000 acres.