Question: Given the following passage  "Remodelling of the structure began in 1762. After his accession to the throne in 1820, King George IV continued the renovation with the idea in mind of a small, comfortable home. While the work was in progress, in 1826, the King decided to modify the house into a palace with the help of his architect John Nash. Some furnishings were transferred from Carlton House, and others had been bought in France after the French Revolution. The external façade was designed keeping in mind the French neo-classical influence preferred by George IV. The cost of the renovations grew dramatically, and by 1829 the extravagance of Nash's designs resulted in his removal as architect. On the death of George IV in 1830, his younger brother King William IV hired Edward Blore to finish the work. At one stage, William considered converting the palace into the new Houses of Parliament, after the destruction of the Palace of Westminster by fire in 1834.",  answer the following question. Note that the answer is present within the text.  Question: who was King Willam IV brother?
Answer:
George IV