Lady Cecilia Knutsdotter was a medieval Swedish mighty and wealthy noblewoman of high nobility. She is known as hertigsdotter, Duke's daughter.

She is mentioned as daughter of the "Duke Canute", and historians differ who that exactly was. For hypotheses, see below. The somewhere in genealogies floating idea that Cecilia's mother were a daughter of king Canute I of Sweden

Canute I of Sweden

Canute I, Swedish: Knut Eriksson , was king over all of Sweden from 1173 to 1195...

 lacks all historical support and must therefore be discarded as unattested romantics.

Cecilia married Geatish lord Filip, who became ancestor of the famed Aspenäs noble house whose Arms depicted lejonörn (= Griffin

Griffin

The griffin, griffon, or gryphon is a legendary creature with the body of a lion and the head and wings of an eagle...

). Historians differ also over whose child Filip was, what was his correct patronymic and what was his seat manor. After Filip's death, Cecilia lived plenty of years as rich widow; a benefactor of monasteries and so forth. Ultimately she was buried beside her husband Filip.

Historians also differ over whether Filip had more than one wife. If he had an earlier wife, then it is not certain that Cecilia was the ancestress of the Aspenäs (lejonörn) nobles. But if she was the only wife, then it is only natural to presume that she is their ancestress (and future generations of the Lejonörn certainly used first names Knut and Cecilia), which makes her an important figure for future generations of that prominent family.

It is presumed that her husband belonged to those who opposed centralized power in Sweden. He seems to have been party in revolts against king Eric XI of Sweden

Eric XI of Sweden

Eric "XI" of Sweden, or Eric the Lisp and Lame Swedish: Erik Eriksson läspe och halte; Old Norse: Eiríkr Eiríksson was king of Sweden in 1222–1229 and 1234–1250.-Background:...

 and against the regent Birger jarl

Birger jarl

, or Birger Magnusson, was a Swedish statesman, Jarl of Sweden and a member of the House of Bjelbo, who played a pivotal role in the consolidation of Sweden. Birger also led the Second Swedish Crusade, which established Swedish rule in Finland. Additionally, he is traditionally attributed to have...

 sometime in the 1240s and 1250s.

Cecilia had attestedly son Birger Filipsson, Lord of Idö, executed by beheading as rebel on 20 August 1280, and daughter Ingegerd Filipsdotter.

Concluded from, among other reasons, the occurrence of the names Knut and Cecilia among Jon's close descendants, her eldest son was Jon Filipsson who was executed as rebel in 1280.

Similarly, she presumably had at least two surviving daughters, of whom it is not known if one of them were the with name attested daughter of hers, Ingegerd: one of those daughters married lord Filip Törnesson, justiciar of Närke, and became great-great-grandmother of children of baron Jon Havtoreson, the Norwegian royal hopefuls; and the other married the rebel lord Karl Tjelveson of Fånö, and became foremother of for example the noble families of Eka and of Frössvik (whose daughters produced regents and kings of Sweden).

Cecilia's father, Duke Canute

Who was that "Duke Knut", Cecilia's historically mentioned father?

Three sufficiently possible and credible alternatives have been proposed:

• jarl Knut Birgersson of the Bjelbo family, Riksjarl of Sweden who was killed in 1208 in battle of Lena
  Battle of Lena
  The Battle of Lena occurred on January 31, 1208, and probably took place near Kungslena , which is located in the Tidaholm Municipality in Västergötland, Sweden....
  
  
• Canute, Duke of Reval
  Canute, Duke of Reval
  Canute or Knud Valdemarsen was a Danish bastard son of King Valdemar II of Denmark, who became Duke of Revelia, Blekinge and Lolland.Canute was the son of the king by his concubine, Helena Guttormsdotter, widow of Danish nobleman Esbern Snare and daughter of the late Guttorm, Riksjarl of Sweden....
  
  , holder of Blekinge
  Blekinge
  ' is one of the traditional provinces of Sweden , situated in the south of the country. It borders Småland, Scania and the Baltic Sea.The name "Blekinge" comes from the adjective bleke, which corresponds to the nautical term for "dead calm"....
  
   in southern borders of Sweden - bastard son of king Valdemar II of Denmark
  Valdemar II of Denmark
  Valdemar II , called Valdemar the Victorious or Valdemar the Conqueror , was the King of Denmark from 1202 until his death in 1241. The nickname Sejr is a later invention and was not used during the King's own lifetime...
  
   and Helena, daughter of Swedish riksjarl Guttorm ("Örnfot")
• jarl Knut Haakonson, claimant of the throne of Norway in late 1220s (leader of Ribbunger party in Norway); son of jarl Haakon Galin (whose father was Folkvid, justiciar of Vermelandia, and mother was Cecilia Sigurdsdottir of Norway, daughter of king Sigurd II) and Kristin Nikolasdottir, daughter of Nikolas Blaka and Karin Eriksdotter of Sweden, daughter of king St.Eric of Sweden.

Knut Birgersson Jarl has been deemed somewhat uneasy choice because of chronological problems. That Knut died 1208, and because of her children's age and her own likely death date, Cecilia firstly need to have been born in the very end of Knut's life (c 1208) when Knut was already elderly (and several decades after birth of that Knut's other attested child/children); and even that makes Cecilia somewhat old for her own marriage and to give birth to her attested children, at last one of whom was executed in 1280 and Cecilia possibly was then living. Additionally, name Cecilia appears not in Knut's immediate family nor his direct ancestry.

Duke Canute is uneasy choice because his descendants married with presumed descendants of Cecilia in generations that were Cecilia his daughter and ancestress of that issue, there would have been a marriage of a lady and her first cousin's son, something not almost ever dispensated in those centuries by church. Additionally, name Cecilia appears not in that Knut's family nor his ancestry.

Finally, claimant Knut Haakonson of Ribbunger, earl of Norway, is uneasy choice (though possibly easiest of these) because he was not generally called duke. He probably would be called king, or earl, or lord, or master, but not easily duke which title was adopted to Norway in Knut's and Cecilia's lifetime as higher than earl (actually, to Knut's father-in-law duke Skule). However, his recognized title jarl is translated as Dux at least in Sweden. The name Cecilia certainly is present in that Knut's ancestry.