By Michael Holden and Sachin Ravikumar LONDON (Reuters) – King Charles and his siblings stood vigil by the coffin of their late mother Queen Elizabeth on Friday as tens of thousands of mourners queuing to pay their final respects during her lying in state were told they faced a wait of up to 24 hours. Charles, Princess Anne, Princes Andrew and Edward, attired in military uniforms, stood in silence with their heads bowed for the 15-minute vigil at the historic Westminster Hall where the coffin of the late monarch has been lying since Wednesday. Most of the other members of the British royal fam…