Complex sentence: His father was a successful businessman and engineer who served in the British Army in the First World War and his uncle was a Destroyer commander who had a successful war fighting German U-Boats in the First Battle of the Atlantic.
Split into simpler sentences: His father was a successful businessman and engineer who served in the British Army in the First World War. His uncle was a Destroyer commander who had a successful war fighting German U-Boats in the First Battle of the Atlantic.