Question: Who is the uncle of Robert De Brus, 4Th Lord Of Annandale?
Answer: Robert III de Brus

William de Brus, 3rd Lord of Annandale (died 16 July 1212), was the second but eldest surviving son of Robert de Brus, 2nd Lord of Annandale. His elder brother, Robert III de Brus, predeceased their father, never holding the lordship of Annandale. William de Brus thus succeeded his father when the latter died in 1194