Complex sentence: Their financial problems are exacerbated once Sport's grandfather Simon Vane (from his mother's side) becomes terminally ill and stops sending his regular payments, however things change for the better once Sport's father meets the kind Kate who becomes a good stepmother.
Split into simpler sentences: Their financial problems are exacerbated once Sport's grandfather Simon Vane (from his mother's side) becomes terminally ill and stops sending regular payments to Sport. Tthings change for the better once Sport's father meets the kind Kate who becomes a good stepmother.