Why didn't Robert son of William I become King?

Answer 1

King William I of England (William the Conqueror) had been king of England since his victory at The Battle of Hastings in 1066. He had previously been, and still was, Duke of Normandy - the North Western part of France. He had four sons, Robert born around 1051, Richard, born about 1055,William born around 1056 and Henry, born about 1068. He also had a daughter, Adela, born about 1062, and his second son, Richard died in 1081. It would have been the custom for the oldest son, Robert, to inherit the crown of England on his father's death but King William decreed on his deathbed in 1087, that Robert would become Duke of Normandy and his second son, William would become King of England. William II became king in 1087 and was succeeded by his younger brother, Henry I in 1100. Henry reigned until his own death in 1135.