Complex sentence: Gloucester became ill with convulsions when he was three weeks old, so his mother moved him into Craven House, Kensington, hoping that the air from the surrounding gravel pits would have a beneficial effect on his health.
Split into simpler sentences: Gloucester became ill with convulsions when he was three weeks old. Therefore, his mother moved him into Craven House, Kensington, hoping that the air from the surrounding gravel pits would have a beneficial effect on his health.