Brotherly rivalry between India’s billionaire Ambani brothers is threatening to derail one of the biggest tie-ups in the history of emerging markets telecoms – between Reliance Communications and South African mobile operator MTN.

Reliance Communications, India’s second-largest mobile company headed by Anil Ambani, revealed on Friday night that Reliance Industries, controlled by Anil’s elder brother Mukesh Ambani, has claimed right of first refusal in any takeover of the cellular carrier.