Princess Hemvadi, informally known as Sadet Phra Ong Hem, was the youngest daughter of King Chulalongkorn and Hem Amatayakul (daughter of Phraya Thammasarnniti Wichitphakdi. She was born on 12 January 1892. Originally named Princess Mandhanabhavadi, her father, King Chulalongkorn, renamed her Princess Hemvadi on 8 January 1898 when she was six years old.