Complex sentence: However, the family's wealth was wiped out in the crash of 1929 and they had to move back to Canada, where he became Vice-President of the McColl-Frontenac Oil Company.
Split into simpler sentences: However, the family's wealth was wiped out in the crash of 1929 and they had to move back to Canada. He returned to Canada and became Vice-President of the McColl-Frontenac Oil Company.