Adela (Ela) was from Warenne and of the Plantagenet Dynasty, known as Adela Plantagenet de Warenne or as Ela de Warenne.

From Medlands:

http://fmg.ac/Projects/MedLands/ENGLISH%20NOBILITY%20MEDIEVAL.htm#dauHamelinMistJohnEngland

ELA de Warenne ([1162]-after 1220).  The primary source which confirms her parentage and two marriages has not yet been identified.   m firstly ROBERT de Newburn, son of ---.  m secondly WILLIAM Fitzwilliam of Sprotbrough, Yorkshire, son of --- (-[1219/24]).  

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1. D: I29770
2. Name: Suzanne Warren [Concubine #5]
3. Surname: Warren
4. Given Name: Suzanne
5. Suffix: [Concubine #5]
6. Sex: F
7. Birth: ABT 1166 in England 1 2
8. Death: WFT Est 1183-1266 1 2
9. _UID: 43AE95A41445DF4A9967369D4068E4AFBAB0 3 4 5 1 6 7 8 9 2 10
10. Change Date: 24 Oct 2006 at 19:01:02

Father: Hamelin Plantagenet b: 1130 in Normandy, France c: in Anjou?

Mother: Isabel Warren b: 1137 in Warren, Surrey, England c: in England - Only Dtr And Heir Earl Of Surrey

Marriage 1 John I "Lackland" Plantagenent King of England b: 24 Dec 1167 in Beaumont Palace, Oxford, England c: in France (Count Of Mortain)

   * Married: WFT Est 1183-1208 in Unmarried 1 2

   * Sealing Spouse:

   * Event: Seal 1 2 2

   * Event: Seal 1

Children

  1. Has Children Richard Fitz Roy b: ABT 1186 in Chilham Castle, Kent, England

Marriage 2 Spouse Unknown

   * Married: WFT Est 1183-1208 in Unmarried 2

   * Sealing Spouse:

   * Event: Seal 2

   * Event: Seal 2

Sources:

  1. Title: #671

     Text: Date of Import: Dec 26, 2000

  2. Repository:

           Name: Not Given

     Title: v11t4329.FTW

     Note:

     Source Media Type: Other

     Text: Date of Import: Dec 26, 2000

  3. Title: #678

     Text: Date of Import: Jul 5, 2000

  4. Title: #680

  5. Title: #679

     Text: Date of Import: Dec 15, 2000

  6. Title: #688

     Text: Date of Import: Apr 24, 2001

  7. Repository:

           Name: Not Given

     Title: Ball.FTW

     Note:

     Source Media Type: Other

     Text: Date of Import: Jul 5, 2000

  8. Title: Ancestral File (TM)

     Author: The Church of Jesus Christ of Latter-day Saints

     Publication: July 1996 (c), data as of 2 January 1996

  9. Repository:

           Name: Not Given

     Title: 401017.ftw

     Note:

     Source Media Type: Other

     Text: Date of Import: Dec 15, 2000

 10. Repository:

           Name: Not Given

     Title: 160010.GED

     Note:

     Source Media Type: Other

     Text: Date of Import: Apr 24, 2001 

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From:

http://fmg.ac/Projects/MedLands/ENGLAND,%20Kings%201066-1603.htm#_Toc159664195

Mistress (1): --- de Warenne, daughter of HAMELIN d'Anjou Earl of Surrey & his wife Isabelle de Warenne . According to Given-Wilson & Curteis[475], one of the mistresses of King John was the "sister of William de Warenne" but the authors do not specify which sister she was. The primary source which confirms her relationship with John has not yet been identified.

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John's cousin and mother of his illegitimate son, Richard FitzRoy.

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John had the following illegitimate children:

Joan, Lady of Wales, the wife of Prince Llywelyn Fawr of Wales, (by a woman named Clemence)

Richard Fitz Roy, (by his cousin, Adela, daughter of his uncle Hamelin de Warenne)

Oliver FitzRoy, (by a mistress named Hawise) who accompanied the papal legate Pelayo to Damietta in 1218, and never returned.

By an unknown mistress (or mistresses) John fathered:

Geoffrey FitzRoy, who went on expedition to Poitou in 1205 and died there.

John FitzRoy, a clerk in 1201.

Henry FitzRoy, who died in 1245.

Osbert Gifford, who was given lands in Oxfordshire, Norfolk, Suffolk, and Sussex, and is last seen alive in 1216.

Eudes FitzRoy, who accompanied his half-brother Richard on Crusade and died in the Holy Land in 1241.

Bartholomew FitzRoy, a member of the order of Friars Preachers.

Maud FitzRoy, Abbess of Barking, who died in 1252.

Isabel FitzRoy, wife of Richard Fitz Ives.

Philip FitzRoy, found living in 1263.

(The surname of FitzRoy is Norman-French for son of the king.)

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Adela was not his wife, she was his mistress. They were cousins.