Question: Where was Osbert Sitwell's sibling educated?

Knowledge 1: The Sitwells
The Sitwells (Edith Sitwell, Osbert Sitwell, Sacheverell Sitwell), from Scarborough, North Yorkshire, were three siblings who formed an identifiable literary and artistic clique around themselves in London in the period roughly 1916 to 1930. This was marked by some well-publicised events, notably Edith's "Façade" with music by William Walton, with its public debut in 1923. All three Sitwells wrote; for a while their circle was considered by some to rival Bloomsbury, though others dismissed them as attention-seekers rather than serious artists. [SEP] Knowledge 2: Reresby Sitwell
The elder son of Sir Sacheverell Sitwell, 6th Baronet, he was educated at Eton College and King's College, Cambridge, but left the latter of his own volition without a degree. He married Penelope Forbes, the niece of Bernard Forbes, 8th Earl of Granard, in 1952. He was succeeded in the baronetcy by George Sitwell, the son of his brother Francis, who died in 2004.
Knowledge 1: The Sitwells
The Sitwells (Edith Sitwell, Osbert Sitwell, Sacheverell Sitwell), from Scarborough, North Yorkshire, were three siblings who formed an identifiable literary and artistic clique around themselves in London in the period roughly 1916 to 1930. This was marked by some well-publicised events, notably Edith's "Façade" with music by William Walton, with its public debut in 1923. All three Sitwells wrote; for a while their circle was considered by some to rival Bloomsbury, though others dismissed them as attention-seekers rather than serious artists. [SEP] Knowledge 2: Elizabeth II
Elizabeth's only sibling, Princess Margaret, was born in 1930. The two princesses were educated at home under the supervision of their mother and their governess, Marion Crawford. Lessons concentrated on history, language, literature and music. Crawford published a biography of Elizabeth and Margaret's childhood years entitled The Little Princesses in 1950, much to the dismay of the royal family. The book describes Elizabeth's love of horses and dogs, her orderliness, and her attitude of responsibility. Others echoed such observations: Winston Churchill described Elizabeth when she was two as "a character. She has an air of authority and reflectiveness astonishing in an infant." Her cousin Margaret Rhodes described her as "a jolly little girl, but fundamentally sensible and well-behaved".
Knowledge 1: The Sitwells
The Sitwells (Edith Sitwell, Osbert Sitwell, Sacheverell Sitwell), from Scarborough, North Yorkshire, were three siblings who formed an identifiable literary and artistic clique around themselves in London in the period roughly 1916 to 1930. This was marked by some well-publicised events, notably Edith's "Façade" with music by William Walton, with its public debut in 1923. All three Sitwells wrote; for a while their circle was considered by some to rival Bloomsbury, though others dismissed them as attention-seekers rather than serious artists. [SEP] Knowledge 2: William Fitz Osbert
William Fitz Osbert or William with the long beard (died 1196) was a citizen of London who took up the role of "the advocate of the poor" in a popular uprising in the spring of 1196. Popular revolts by the poor and peasants in England were rare in the 12th century, and quickly and easily suppressed. The fullest known account of the revolt of 1196 comes from the contemporary English historian William of Newburgh in his "Historia rerum anglicarum" from a chapter entitled "Of a conspiracy made in London by one William, and how he paid the penalty of his audacity".

Answer: Eton College