Complex sentence: His parents were "The Flying Johnsons", a Flying Circus act with the Sells Floto Circus; it was a profession that his father attempted to train him in, but Frank's fear of heights became a problem.
Split into simpler sentences: His parents were "The Flying Johnsons", a Flying Circus act with the Sells Floto Circus. It was a profession that his father attempted to train him in as well but Frank's fear of heights became a problem.