This is a perfect example of a Reynolds Grand Style portrait. It was commissioned by Luke Gardiner of Dublin who was at that time engaged to Elizabeth Montgomery, the central figure of the three. The Montgomery sisters were brought up in Ireland and became known as 'The Irish Graces' because of their beauty. Marrying one of such a trio Luke Gardiner no doubt decided to include the other two in the painting. The picture has often been known as 'The Three Graces', but Reynolds has not in fact depicted the sisters as the three Greek goddesses. However, they are in the vaguely classical costume that Reynolds considered appropriate for this kind of picture, as well as in a classical setting, and some flattering implication remains. In his letter of commission to Reynolds, Luke Gardiner asked for the sisters to be painted 'representing some emblematical or historical subject' the choice of which he left to the artist's 'genius and poetic invention'. Reynolds was noted for his ability to find an appropriate subject for a Grand Style portrait and in this case he has shown the three sisters paying homage to the Greek god of marriage, Hymen. The sister on the right, in white, is Anne who was married just before the picture was commissioned. It is possible that for that reason Reynolds placed her to the right of the god - 'past the post', as it were. Barbara, the youngest sister, on the left, was married the following year. Reynolds wrote to Gardiner saying that the subject 'affords sufficient employment to the figures and gives an opportunity of introducing a variety of graceful historical attitudes'. In accordance with Reynolds's methods of raising the status of portraiture to the level of the Grand Style these 'historical attitudes' are derived from a number of distinguished old masters, including Poussin and Rubens. The old master engraving that Reynolds must have used can be seen in 'The Conjuror' [Tate Gallery T00938], a painting by Nathaniel Hone satirising this practice of Reynolds, although it was and is perfectly acceptable; Hone was probably indulging a fit of jealousy at Reynolds's success.
Simon Wilson, Tate Gallery: An Illustrated Companion, Tate Gallery, London, revised edition 1991, p.33