Oldest Billionaire: The legacy that Keshub Mahindra left behind will endure for a very long period of time. A few days after Forbes included him on its list of India's wealthiest billionaires for 2023, the terrible news came out. In India, Keshub Mahindra was the oldest billionaire with a net worth of more than Rs 10,000 crore, according to the most recent Forbes list of the world's richest people.