Complex sentence: Although Constable was his parents' second son, his older brother was mentally handicapped and so John was expected to succeed his father in the business, and after a brief period at a boarding school in Lavenham, he was enrolled in a day school in Dedham.
Split into simpler sentences: Although Constable was his parents' second son, his older brother was mentally handicapped and John was expected to succeed his father in the business. After a brief period at a boarding school in Lavenham, he was enrolled in a day school in Dedham.