While David will be playing his second year in the HIL, Conor will feature for the first time this season.
In the recently concluded HIL Players' Closed Bid 2014, David was bought for USD 51,000, making him the second most expensive goalkeeper in the league this season after PR Sreejesh.
Conor's signing (USD 10,000) for the same team makes him only the second Irish person to ever play in the league and mark a high point for the twin brothers.
He was also adjudged the 'Best Goalkeeper of the Tournament' in the FIH Champions Challenge 2014, held in Kuantan, Malaysia, where Ireland finished at fourth position.
Speaking on his brother Conor, who has 137 international caps, David said, "Since the news of joining a new team together, we both are very happy and excited to play alongside for Dabang Mumbai. On top of that, I have experienced the electric atmosphere at the games which is something I can't wait for, the chance to be able to play in front of 10,000 screaming fans who love the game.