Welcoming him into the party-fold, Modi said he will further strengthen the party.
"Today, Prime Minister Manmohan Singh's brother Daljeet Singh has joined BJP. This will further strengthen us. We are not a party which talks of membership but one which forms relations," Modi said.
Kohli, a local businessman, was welcomed by Badal and BJP's candidate from Amritsar Arun Jaitley.
PMO sources said Manmohan Singh's family was "shocked" at the development. "His intentions are not known but he is free to pursue his political career," they said, adding the Prime Minister and Kohli have not been keeping in touch since long.
The sources said Manmohan Singh is the only son and has six sisters. Daljit Singh is the half-brother of the Prime Minister. Manmohan Singh's mother died at an early age.