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 was assassinated on this day in 1991 in a suicide bomb attack by Liberation Tigers of Tamil Eelam (LTTE) during an election rally at Sriperumbudur in Tamil Nadu.
Rajiv Gandhi served as the Prime Minister from October 31, 1984 to December 2, 1989.