Who was

ROBERT FITZROY ,

1st Earl of Gloucester's mother?

 

She is legally unknown.

She is said to be either Nest Princess of Deheubarth or the daughter of Rainald Gay of Hampton Gay or possible Sibyl Corbet, Lady of Alcester.

What is known is that he is the eldest offspring of Henry I.

That being so, it is unlikely his mother was Sibyl, as she was his 5th mistress. Whereas, Robert's mother may have been his first 'concubine, as Robert was born before Henry became king and was married to Matilda of Scotland . ( who is also our ancestor , as Empress Matilda is their legitimate daughter)

Princess Nest was around at this time ( Henry's I youth) in the royal court being held hostage by Henry's brother William Rufus, King of England at the time. She would have been about 15 years old. William is the 3rd son of William The Conqueror and Henry is the 5th son. Date wise, Robert is said to be born 1090, Nest was the royal hostage in the 1090s and Henry would have been 25 years old having been born in 1068. All these factors and that we can find nothing much about  the daughter of Rainald Gay being around Henry I in 1090, points to quite possibly Nest being Roberts mother, although not acknowledge by her ( perhaps the sex was not mutually willing?) 

She also bore another son to Henry I ,his name was Henry Fitz Henry b. c. 1103. 

( Henry Fitzroy) Implying he was recognised. So why not recognise Robert?

This is the argument on the debate.

So in conclusion Robert's mother could have been Nest or the daughter of Rainald Gay.

Either way he is still our ancestor.