1) Hari's family is poor, and after he leaves his sister becomes responsible for taking caring of the family.
The Desilva's are wealthy and have a summer home near Hari's family home.
2) Socially, Hari's family would be considered inferior to the De Silva family. Hari once worked for the family, and his sister took over for him after he left. The De Silva's are kind and have the finances to help.