Complex sentence: Steph becomes a babysitter to Tom, and later begins a relationship with his older brother, Max Cunningham, follow by his separated to his marriage to Claire, they get engaged, but have an on-off relationship fraught with frequent arguments.
Split into simpler sentences: Steph becomes a babysitter to Tom, and later begins a relationship with his older brother, Max Cunningham. They get engaged, but have an on-off relationship fraught with frequent arguments.