The works by Dante Gabriel Rossetti were seen by Guy Schwinge of Duke's in the home of direct descendants of the Liverpool-born ship owner and art collector Frederick Leyland (1831-92).
A small oil The Monna Rosa (1867) depicts Leyland's wife with tumbling auburn locks arranging flowers in a blue and white Chinese vase, while the coloured chalk bust portrait of 1870 shows Leyland himself.
The largest of the trio is a second version of The Salutation of Beatrice (the other now in Toledo Museum of Art, Ohio). Depicting Jane Morris in the role of Beatrice Portinari, the subject of the painting is derived from the theme of unrequited love in Dante's Vita Nuova.
Schwinge said: "To find a single Rossetti in a house is quite exceptional. To find two major works by the artist and a portrait of his greatest patron is almost unbelievable."
The exhibition runs until June 5.