India's richest man Mukesh Ambani and his brother Anil, who have battled over their father's businesses, have signed a $200m (£142m) telecoms deal.
Correspondents have described the deal as a move towards reconciliation between the billionaire brothers.
Under the deal, separate telecom companies run by the two Ambanis will share networks to speed up 4G services.
The world's richest brothers have fought bruising court battles in the past over natural gas interests.
Relations became strained during a dispute over the division of the conglomerate left by their father, Dhirubhai, who died in 2002 without a will.
In the first signs of a thaw, in 2010, the brothers abandoned a non-competition agreement that prevented them for entering the same businesses.
In 2011, they came together to dedicate a memorial to their father and their mother, Kokilaben, told reporters: "There is love between the brothers".
"The optic fibre contract may well be the start of deepening business relations between the two brothers - one active in big-ticket infrastructure but with significant debts and the other with plenty of cash to invest in new projects," The Hindu newspaper commented.
Mukesh Ambani is chairman and managing director of Reliance Industries, one of the largest conglomerates in the world, and also owns the Indian Premier League team, the Mumbai Indians.
Anil Ambani has substantial interests in power, infrastructure and finance.
The Reliance empire was divided between the two brothers in 2005 after a bitter seven-month feud.