His marriage to Margaret was arranged while he was still a child. She was the heiress of Maine. However, Margaret died before the marriage took place.

He was very brave and possessed great skill in military exercises but he tended to be a little lazy and weak of character which caused the King of France and the nobles to be unsatisfied with him. They stirred up strife with his father, William the Conqueror. Robert quarreled with his father and brothers because he did not like his share of power.

Robert became rebellious and the Conqueror allied himself with the King of France to stop his son. Queen Matilda was secretly sending Robert money and the Conqueror was very displeased when he discovered the fact. Queen Matillda made great effort to reunite father and son which occurred at Easter 1080. Their truce lasted until 1083.

After Matilda's death, Robert left the court and spent a few years wandering through Flanders, France & Germany. He fathered several illegitimate children. Richard was one of them. He spent time with his uncle King Rufus and was killed in a hunting accident in New Forest in 1099.

King William, at his death, had divided his kingdom and granted the Duchy of Normandy to Robert and the Kingdom of England to William Rufus.

Robert went to the Holy Land on a crusade in 1096. Robert had become very poor from his mismanagement of money. Some reports say that he often stayed in bed because he did not have clothes. He needed to raise money for his crusade so he mortageged his duchy for 10,000 marks to his brother William Rufus.

The two brothers had agreed to name each other the Heir to their throne if one of them died. William Rufus died 2 Aug 1100 and Robert was supposed to have inherited the throne of England. However, Robert was on his return trip from the crusade and married a wealthy young girl, Sibylla verch Geoffrey in May 1100 in Apulio, Italy, in order to have the money to buy back his duchy from William. He had not yet returned when William died. Therefore, in his absence, Henry II, his younger brother usurped the crown of England.

Robert planned an invasion to get the crown for himself but he was not a very good general and he mishandled the military tactics and Henry was able to resist the invasion. He was then forced to sign the Treaty of Alton giving up any claim to the throne of England.

Henry went to France in 1106 and defeated Robert's army at the Battle of Tinchebray and claimed Normandy as a possession of England. Robert was captured and put in prison in Devizes castle for 20 years. He then moved to Cardiff Castle where he died in 1134. He was in his early 80's at the time of his death.