The Missing Brontë

The famous ‘pillar portrait’ of Charlotte, Emily and Anne Brontë hangs in the National Portrait Gallery, London. Its name derives from the overpainted space between Charlotte and Emily, which originally held the likeness of the painter, their 17-year old brother Branwell. So, who is this missing sibling, the only one of this intense, wondrous family who is not acknowledged as a literary legend, and who had a central place in their group portrait, only to erase himself?