Complex sentence: Hannah left young Isaac in the care of her parents, James and Margery Ayscough, when he was three years old when she moved to North Witham (one mile away) to marry vicar Barnabas Smith.
Split into simpler sentences: Hannah left young Isaac in the care of her parents, James and Margery Ayscough, when he was three years old. At that time she moved to North Witham (one mile away) to marry vicar Barnabas Smith.