Cawley gives Judith de Bretagne an estimated birth year of 982. By contrast, Baldwin simply states that her date and place of birth are unknown. 
Her father was Conan I, d. 27 June 992, count of Rennes, count (princeps) of Brittany. Cawley adds detail that he as Conan I "le Tort", Duke of Brittany
Her mother was Ermengarde,  d. aft. 992, daughter of Geoffrey I, count of Anjou. 
Cawley reports that Judith married, at Mont Saint-Michel, in about 1000, as his first wife, Richard II "le Bon/l'Irascible" Comte de Normandie, son of Richard I "Sans-Peur" Comte de Normandie & his second wife Gunnora, who died 28 Aug 1027. 
Baldwin places Judith's marriage within the time period when Richard II and Judith's brother Geoffrey of Brittany were both ruling, thus after 996 (the date of Richard I's death) and before 1008 (the date of Geoffrey's death). Baldwin states that she married Richard II, duke of Normandy, who died d. 23 August 1026, duke of Normandy. 
Douglas (1950), 289-291) asserts that the marriage probably took place well before 1008. Richardson also states that Judith married before 1008, as his first wife, Richard II, Duke of Normandy, 996-1026, son and heir of Richard I, Count (or Prince) of the Normans, by his second wife, Gunnor. 
1012 Subscription to Charter for Exchange of Land
Cawley reports that an agreement between the abbots of Jumièges and Bougeuil concerning an exchange of land in Poitou, by charter dated 13 Apr/4 Apr 1012, is subscribed by "Richardus…filius Ricardi principi magni…Judith…" 
Judith was a major donor of the convent of Sainte Marie at Montivilliers, which had been founded under the Merovingians and destroyed by vikings in the ninth century. Judith's father-in-law, Duke Richard of Normandy, had wanted to establish a monastery , and the best location, at Fecamp, was already occupied by a convent, so he rebuilt Montevilliers and moved the women there to free up the location at Fecamp for a monastery. 
Cawley states that Judith died 16 June 1017; the Chronicle of Caen Saint-Etienne records the death in 1017 of "Judita comitissa"  Richardson and Baldwin both give the date as 28 June, 1017
Her place of death is unknown,  but richardson gives her burial site as Bernai Abbey. 
1017 Remarriage of Richard
After Judith's death, Richard married, secondly, probably soon after 1017, Papia. They had two sons, Mauger, Archbishop of Rouen, and Guillaume, Count of Arques. Richard II, Duke of Normandy, died at Fecamp 23 August 1026.
If the marriage was in the year 1000 and Judith died in 1017, her children would have been born between these dates.
Judith de Rennes  and Richard had three sons and three daughters
[[Normandie-43|Robert] I] "le Magnifique," Duke of Normandy. was born, say, 1003. Baldwin  states that his date and place of birthg are unknown. Wikitree, without source, gives a place and date of Rouen June 22 ,1000,  which has been widely repeated. He died between 1 and 3 July, 1035 
Guillaume born, say, 1005, was a monk at Fecamp, He died about 1025. 
Unknown daughter, born, say, 1007 married Baldwin IV,Count of Flanders after 1030. He was also known as Baudouin IV "le Barbu/Pulchrae Barbae" Count of Flanders (980 - 30 May 1035; his parents were Arnoul II "le Jeune," Count of Flanders and Rozala di Ivrea). Cawley notes that she has sometimes been called Eleanor (or Ainor) or Judith in late secondary sources, but there does not seem to be a good primary source that gives her name. For the interesting (but unproven) conjecture that this daughter was the same person as Ainor, later wife of Geoffrey, viscount of Thouars, see Beech (1986). This marriage of Baldwin IV is also discussed on the page of Judith of Flanders.  So her identiy as "Eleonore" de Normandie is unproven. .
Unknown daughter: GND states only that the third daughter of Richard and Judith died as an adult virgin and does not given her name. ,  Cawley advises review of Stasser (1990) for the identification of this daughter with the Mathilde, daughter of count Richard, whose death is entered under the year 1033 in the Annals of Rouen.  Richardson identifies this daughter with Mathilde.
↑ 3.03.13.23.3 Charles Cawley, Foundation for Medieval Genealogy. Medieval Lands Database. Judith de Bretagne Brittany Accessed June 12, 2017. jhd
↑ 4.04.14.24.184.108.40.206.74.84.9 Guillaume de Jumièges, Gesta Normannorum Ducum, as edited in Elisabeth van Houts, ed. & trans., The Gesta Normannorum Ducum of William of Jumièges, Orderic Vitalis and Robert of Torigni, 2 vols., (Oxford, 1992). GND iv, 13 (vol. 2, pp. 28-9) (Citation is by book and chapter of Guillaume's work, with the volume and page number of the edition by van Houts in parentheses. Unless otherwise stated, references are to Guillaume's work, and not to later additions by such authors as Orderic Vitalis and Robert de Torigni.) Cited by Stewart Baldwin. The Henry Project. Judith de Bretagne Uploaded 17 December 2005. Accessed June 12, 2017 jhd
↑ The Angevin genealogical collection states that Judith, wife of Richard of Normandy, was the daughter of Conan by his wife Ermengarde, daughter of Geoffroy of Anjou [Poupardin (1900), 208]. Cited by Stewart Baldwin. The Henry Project. Judith de Bretagne Uploaded 17 December 2005. Accessed June 12, 2017 jhd
↑ Cawley notes that Guillaume of Jumièges records the marriage of “dux Richardus” and “Goiffredum Britannorum comitem...sororem...Iudith” at “limina Archangeli Michaelis” Cited by Charles Cawley, Foundation for Medieval Genealogy. Medieval Lands Database. Judith de Bretagne Brittany Accessed June 12, 2017. jhd
↑ Chron. Rothomag., RHF 10, 322 (year only); Ex Obituario Gemmeticensi, RHF 23, 420 (28 June); Notæ Monasterii Montis Sancti Micaelis, RHF 23, 579 (28 June)] Other death dates in the same month have been offered for Judith, but the evidence for these dates is unclear. [e.g., Breese (1988), 208 (17 June 1017); ES 2, 79 (16 June 1017) Cited by Stewart Baldwin. The Henry Project. Judith de Bretagne Uploaded 17 December 2005. Accessed June 12, 2017 jhd