This is another chapter where outsiders ignore the existence of the sister, who should be the main person they talk to as she is already in college. At the same time he always talks like she is with her, so I doubt that the parents would just send their basket case of a son (standing in front of an empty chair while waiting for the air to use a pc and talking to himself, in case the sister was not really there) to look after his dementia stricken grandma.