The second earliest (to the Bolton Castle mare) thoroughbred family foundation mare, Old Bald Peg (probably foaled 1645c) is located at Helmsley, Yorkshire, indicating she may be a descendant of mares belonging to the first Duke of Buckingham, George Villiers (1592-1628) who acquired the estate at Helmsley through marriage to the Earl of Rutland's daughter in 1620. "Bald" or "Ball'd" at the time possibly meant a round, bulging forehead, with a white marking, which possibly extended as far down as the lips, supporting Old Bald Peg being an Arabian, although her origins are uncertain, different sources describing her as an Arabian and a Barb.

Dam of Old Morocco Mare through which the maternal line of the family continues and also the dam of Spanker, important sire and described as the best racehorse at Newmarket in the time of Charles II; Charming Jenny (dam of Betty Percival, Highland Laddie, Hampton Court Charming Jenny and Leedes); and Young Bald Peg (grandam of top class racehorse and twice Champion Sire Fox)