Joseph and Donnacha O'Brien will put sibling rivalry aside to take on the best of British in next year's new-look Racing League.
The rising star trainers have enjoyed a 2020 to remember with Joseph, 27, winning the Melbourne Cup for the second time with Twilight Payment at Flemington this month.
And his 22-year old younger brother, in his first year training since hanging up his saddle, scorched to a maiden Classic success when Fancy Blue won the Prix de Diane, the French Oaks, at Chantilly.
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The six-week long 1.8m (UK Pound) league will see six teams, made up of three jockeys and 30 horses, clash over 36 races, over varying distances, worth Â£50,000 and 1,000 points each.
Jockeys will wear team colours in the competition, which will be held at Doncaster, Newcastle, Lingfield and Windsor throughout the summer holidays.
"We're really pleased to get the O'Briens as a team from Ireland," said Championship Horse Racing chief executive Jeremy Wray.
"Having trainers in the same geographical area was the logical first step. We've got a broad representation with teams from the north and south."
Northern-based trainers Richard Fahey and Tim Easterby will join forces, while Charlie Fellowes, Hugo Palmer and George Scott form a powerful 'Newmarket' team.
Wiltshire-based trainers Roger Charlton, Alan King, Martyn Meade and Brian Meehan combine as do a powerful looking combination of Classic winning trainers Andrew Balding and Richard Hannon.
George Baker, David Menuisier, Gary Moore and Amanda Perrett also make up a team.
Six more teams are expected to be added in the weeks ahead, plus news on how jockeys will be drafted.
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