Hautboy Mare is the second earliest mare in the lineage of the maternal line of Family 12 descending from Foundation Mare Brimmer Mare

Dam of Old Montagu Mare (by [Darcy's] Montagu) through which the maternal line of the family continues

Ancestress of many high class horses including as 4th dam of Magog (1778 Jockey Club Plate, Great Subscription Purse [5yo division] York);

and most notably as the 4th dam of the peerless Eclipse, the greatest racehorse of the 18th century, unbeaten winner of 18 races including 12 King's Plates, second in the list of leading sires 11 times, every year from 1778 and 1788, and progenitor of the Darley Arabian male line from which over 95% of the world's current thoroughbreds descend