Hari Singh was born on 23 September 1895 at the palace of Amar Mahal, Jammu. He was the only surviving son of Raja Amar Singh, the brother of Maharaja Pratap Singh, then the Maharaja of Jammu and Kashmir. Since the Maharaja had no issue, Hari Singh was heir to the throne of Jammu and Kashmir.
In 1930, Hari Singh attended the First Round Table Conference in London. He suggested that the Indian Princely states should join an “All India Federation” and pleaded for equal status for Indians in the British Commonwealth of Nations. While replying to the inaugural address by King-Emperor George V, Hari Singh said "I must express our deep gratitude to His Most Gracious Majesty for the cordial welcome tendered to us and I pray that providence may grant us the vision and the will to realize the hopes expressed in the inspiring words uttered this morning by our beloved Emperor. This is the first occasion on which the Princes of India meet in person at a Conference Table along with the representatives of British India and His Majesty's Government to discuss the political future of India. ... I feel deeply gratified at the progress which has been made with the scheme of an All-India Federation as worked out in the Report of the Federal Structure Sub-Committee. But ever since the idea of a Federation was taken up in this Conference, some surprise has been expressed in various quarters in India and in England at the willingness of the Princes to join an All-India Federation. It is said that Princes have forced the pace and that in any case they should have opposed a Federation with British India. I have never disguised from my friends, my warm support of the idea of an All-India Federation"