Princess Diana’s brother, Charles Spencer, hired the same divorce lawyer King Charles III used when they dissolved their marriage, RadarOnline.com has learned. Spencer has reportedly hired top U.K. attorney Fiona Shackleton to oversee his divorce from third wife Karen Spencer. Shackleton has built quite the list of A-list celebrities she’s represented over the course of her career, including Paul McCartney and Heather Mills, as well as members of the royal family, such as Prince Andrew and Sarah Ferguson — and most notably, Charles and Diana. Charles and Diana famously separated in 1992, but t…