Siblings to U S Navy Flag and Fancy Blue to face off at Naas on Monday

The battle of the O'Briens will take another twist as Donnacha and Aidan unleash full or half-siblings to July Cup scorer U S Navy Flag and Prix de Diane heroine Fancy Blue in the opening juvenile fillies' maiden at Naas (1.25) on Monday.

O'Brien snr will take the wraps off Contarelli Chapel, a Coolmore-bred daughter of exciting first-season sire Caravaggio who is owned by Westerberg, Magnier, Tabor and Smith.

The two-year-old is out of the winning Sadler's Wells mare Chenchikova and is therefore a half-sister to four black-type winners, including last season's French Classic heroine and Nassau Stakes scorer Fancy Blue.

Fancy Blue, a daughter of the late Deep Impact, was a Listed winner for Aidan O'Brien at two before swapping to Donnacha O'Brien and swooping to two top-level successes. She was also second in the Irish 1,000 Guineas and third in the Matron Stakes.

Chenchikova is herself bred in the purple, being a full-sister to dual Derby winner High Chaparral plus Dante Stakes victor and Secretariat Stakes second Black Bear Island.

Contarelli Chapel is a Caravaggio half-sister to Classic winner Fancy BlueCredit: Scoop Dyga/France Galop

Contarelli Chapel will face an equally well-bred rival in Simply Glorious, who will also run in the same ownership.

Bred by the Coolmore-affiliated Orpendale, Chelston and Wynatt, the daughter of War Front is out of the wonderful Galileo mare Misty For Me - winner of four Group 1s including the Irish 1,000 Guineas and Pretty Polly Stakes - and therefore a full-sibling to European champion juvenile and July Cup hero U S Navy Flag plus multiple top-level winning miler Roly Poly.

The pair will face nine rivals including the Ger Lyons-trained and Juddmonte-owned Juncture, a daughter of Dark Angel and out of the Frankel mare Occurrence, a half-sister to Pretty Polly winner Promising Lead and dual Group 3 scorer Visit, a daughter of Oasis Dream.

The penultimate three-year-old fillies' maiden (4.35) will see the Ballydoyle-trained Flora, a daughter of Galileo and Irish Oaks heroine Moonstone, make her debut. The filly is a full-sister to Derby runner-up US Army Ranger and a three-parts sister to dual Group 3 winner Nelson among five black type performers.

Among her 13 rivals in the mile and a quarter contest is the Lyons-trained Party House, a daughter of Camelot who is a close relation to Grand Prix de Paris and Sydney Cup hero Gallante.

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