Just two weeks after his brother Derek passed away, Lord Alan Sugar has revealed that his eldest sister Shirley has also died.The business tycoon, who had a Twitter row with Piers Morgan earlier this year, took to Instagram to announce the heartbreaking news of his sister's death. Alongside a picture of her, the 73 year old wrote on Instagram: "My sister Shirley died today at the age of 88 to join my brother Derek who passed 2 weeks ago.