Joseph Highmore, the son of a coal merchant and the nephew of Thomas Highmore (1660-1720), 'Serjeant-Painter' to the King, was articled to an attorney on 18 July 1707. Bored with his duties, he attended Kneller's Academy from 1713 and in 1715 abandoned law, setting up as a portrait painter in London. From 1720 he attended the St. Martin's Lane Academy, where he was able to study contemporary French styles in art and design, particularly that of Gravelot. He also attended William Cheselden's anatomy lectures and contributed designs to that author's Anatomy of the Human Body (1722). In 1723 Highmore moved to Lincoln's Inn Fields, which lay to the west of the city - a more convenient location for those who needed to find a market for their art. In 1725 he was employed by John Pine (1690-1756) to make twenty drawings for engravings of the recently revived order of the Knights of Bath; among these was his portrait of the Duke of Richmond (Goodwood House, W. Sussex). In 1732 he traveled to the Low Countries to study works by Rubens and van Dyck, and two years later he went to Paris, where he saw the art collections at Versailles and in the Palais du Luxembourg and the Louvre, as well as several important private ones. In the following years he secured commissions from the Royal family, such as Queen Caroline of Ansbach (circa 1735; Royal Collection, Hampton Court).
In the 1740s Highmore's work was increasingly aimed at a middle-class clientele, his popularity with whom was in part due to his ability to capture a likeness in one sitting and to create an informal composition, such as in the present Double portrait of two children in a landscape. This can also be seen in other conversation pieces, such as Mr. Oldham and his Guests (1740s; Tate Britain, London), an unpretentious and unflattering depiction of a group of men seated around a table drinking and smoking. His portraits of An Unknown Man with a Musket (1745; Fitzwilliam Museum, Cambridge) and Samuel Richardson (1747; National Portrait Gallery, London) are further examples of the faithful likeness and unpretentious format sought by such sitters.
Highmore's series of twelve paintings from Pamela of 1744 were designed especially to be engraved and to capitalize on the success of Richardson's eponymous novel (1740-41). Although following the serial tradition of Hogarth's Harlot's Progress and Marriage à la mode, Highmore's Pamela was illustrative rather than inventive, and compositionally simple rather than crowded and complex. The narrative was intended to be read at a glance, not interpreted and considered in the way that Hogarth's narratives were.
Highmore exhibited at the Society of Artists and Free Society in 1760 and 1761. He sold the contents of his studio in 1762 and retired to Canterbury with his daughter and son-in-law. In retirement he pursued a second career as a writer, having begun in 1754 with a critical examination of Rubens's ceiling decorations in the Banqueting Hall, London. In articles written for the Gentleman's Magazine, Highmore further defended Rubens (1766) and examined color theory (1778), postulating the idea that pure, unmixed colors would, from a distance, appear to blend. He also wrote a book on Brook Taylor's Theory of Perspective (1763), and his collection of moral essays (1766) included a consideration of why artists were not the only proper judges of art. His son Anthony Highmore (d. after 1780) was a landscape painter, whose works were occasionally engraved.