Unusually for a woman, Mary Neville is placed on the left side of the pairing, a position traditionally reserved for male authority
A rare portrait of a Tudor family has been acquired by the National Portrait Gallery, in London.
Lady Dacre, and her son, Gregory Baron Dacre, by Hans Eworth, is described as "one of the finest works to be painted in Britain in the mid-16th century".
The gallery paid just under £1m to secure the painting, following a public appeal for donations.
Sandy Nairne, director of the National Portrait Gallery, said: "It is a great acquisition for the nation."
Painted in 1559, the portrait is widely acknowledged as one of the great gems of Tudor portraiture.
Eworth was considered to be the most talented painter working in England following the death of Hans Holbein.
Lady Dacre - Mary Neville - and her son were important members of the nobility with close links to court and the seat of power in Tudor England.
She was the widow of Thomas, 9th Baron Dacre, who had been executed in 1541 and whose titles and honours were forfeited.
Mary remarried, but she continued to campaign for the restoration of honours to her son and his sister, and their titles were restored by Parliament in 1558.
Mr Nairne said: "This powerful painting is unique as one of the earliest surviving double family portraits painted in England and is a remarkable depiction of matriarchal power."
The Gallery acquired the portrait for £997,500 following a contribution of £377,500 from the National Heritage Memorial Fund, a grant of £200,000 from the Gallery's Portrait Fund, and a gift of £300,000 from The Art Fund, as well as other donations.
David Barrie, director of The Art Fund, said the painting offered a "fascinating insight" into the drama of High Tudor society.
He added: "It is right that this outstanding painting, one of the best examples of portraiture from the time, is now a permanent jewel in the Gallery's collection."