They laid flowers and wreaths at the Rajiv Gandhi memorial 'Vir Bhumi' in New Delhi.
Rahul Gandhi, his son and Vice President of Congress tweeted: "Remembering my father today. A leader driven by love, compassion and a deep generosity of heart. We miss him."
Rajiv Gandhi served as the Prime Minister from October 31, 1984 to December 2, 1989.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.