William’s parents were Robert Curthose, the eldest son of William the Conqueror, and Sybilla of Conversano.  She died in 1103 when William was just two. Robert was at that time the Duke of Normandy.   Clito is a latinised form meaning man of royal blood – so similar to prince. He was Count of Flanders by right of his grandmother Matilda, the wife of William the Conqueror.

Alison Weir identifies a legitimate son of Robert Curthose’s called Henry who was killed in a hunting accident in the New Forest but there is no further information and for the most part William Clito is usually identified as Robert’s only legitimate issue.  Robert also had illegitimate sons.  One was called Richard who was killed in the New Forest in 1100.  Richard had a full brother, confusingly enough, also called William and he became the Lord of Tortosa.  It is assumed he was killed around 1110 at the Battle of Jerusalem as there is no further record of him after that.

After the  Battle of Tinchbrai in 1106 which saw Henry I of England defeat Robert Curthose the two brothers travelled to Falaise where William Clito was staying.  Henry had never met his nephew before and he placed the boy in the care of Hélias of Saint-Saëns, Count of Arques who was married to William’s illegitimate half-sister (history does not know her name.)    William remained in their custody for the next four years.  In 1110 Henry sent for his nephew. Hélias was not in residence but his household concealed the boy from Henry’s men and then smuggled him to Hélias who fled Normandy with the boy.

Hélias and William became fugitives.  At first they stayed with Robert de Bellâme but he was captured in 1112.  From there they went to  Baldwin VII of Flanders.  By 1118 many of the nobility of Normandy were sufficiently fed up of Henry I to join William Clito and Baldwin in a rebellion.  However, in the September of that year Baldwin was injured and eventually died.  William  found another sponsor in the form of  King Louis VI of France who invaded Normandy but was comprehensively beaten at the Battle of Brémule on 20th August 1119. Even the Pope interceded on William’s behalf. Despite this the so-called First Norman Rebellion did not improve William’s position.

Disaster struck Henry I when the White Ship sank off Harfleur on the 25 November 1120 drowning his only legitimate son – another William.  This meant that William Clito became a logical successor to his uncle.  He was, after all, the legitimate son of the Conqueror’s eldest son.

In addition to the change in Clito’s  perceived status Henry I  also refused to return the dowry that had come with Matilda of Anjou upon her betrothal to his son.  Matilda’s father, Fulk V Count of Anjou now betrothed his daughter Sybilla to William Clito and gave him as Sybilla’s dowry the county Maine- an area between Anjou and Normandy.  Henry I appealed to the pope and the marriage was ultimately annulled in 1124 because the pair were too closely related.

Meanwhile the Normans had rebelled against Henry for a second time in 1123-1124.

And so it continued, with the French king taking the opportunity to add to Henry I’s discomfort by providing men and money for William in 1127.  It was at this point that William married the french queen’s (Adelaide of Maurienne) half sister Joan of Montferrat.  Louis VI was using William as a pawn against Henry’s claim to Maine.

On the 12 July 1128 William was at the Siege of Aaist.  He was wounded in the arm.  The wound became gangrenous.  He died on 28th July.  Amongst his followers was his brother-in-law Hélias of Saint-Saëns, Count of Arques who had been at his side for most of his life.

It is perhaps not surprising that there is no portrait of William – his uncle  Henry I made a rebel of him and did not want him to inherit either Normandy or England after the death of his own son (also William). Clito’s father, Robert Curthose, survived him by five and a half years.

Weir, Alison. Britain’s Royal Families: the Complete Genealogy