Commentary
Weis says Ragnhild's was the daughter of Olaf of Dublin and Maelcorce.

In his discussion on Ireland, Charles Cawley says: 'The 13th century History of Gruffydd ap Cynan records that he was born in Dublin, son of "Cynan king of Gwynedd and his mother Ragnaillt daughter of Olaf King of the city of Dublin", adding that his maternal grandmother was "Mailcorcre daughter of Dunlang son of Tuathal King of Leinster". From a chronological point of view, it is possible that Ragnhild´s father was Olav son of Sihtric.'

In his discussion on Wales, Charles Cawley says Cynan ap Iago married: 'Ragnhild of Dublin, daughter of Sihtric, King of Dublin.' Since Charles Cawley did not list his source, I am assuming this was a mistake.
Family
ClaimDetailEvidence
FatherAmlaíb mac Sitric (>1013-1034) [S756] [S934] [S1006] [S2728] [S2730]
research
MotherMáelcorcre ingen Dúnlaing (e1013-) [S756] [S1006] [S2728]
research
SpouseCynan ap Iago, Prince of North Wales (e1020-1060) 
Child +Gryffydd ap Cynan, Prince of North Wales (1055-1137) [S756] [S934] [S2730]
research
Attributes
ClaimDetailEvidence
GenderFemale
NameRadnaillt of Dublin [S2730]
research
NameRadnailt of Dublin [S2728]
research
NameRagnhild of Dublin [S934]
research
NameRagnaillt [S756]
research
NameRagnhild [S1006]
research
FatherAmlaíb mac Sitric (>1013-1034) [S756] [S934] [S1006] [S2728] [S2730]
research
MotherMáelcorcre ingen Dúnlaing (e1013-) [S756] [S1006] [S2728]
research
Timeline
ClaimDateDetailAgeEvidence
Birthest 1029 (1029-1034)
 
Sources
IndexTitle
[S756] Weis, Frederick Lewis, "Ancestral Roots of Sixty Colonists Who Came To New England before 1700, 7th Ed." (Genealogical Publishing Co., Inc., Baltimore, 1999).
[S934] Cawley, Charles, "Foundation of Medieval Genealogy (Medieval Lands - Wales)" (2006-7 (v1.1 Updated 12 April 2007)) (https://fmg.ac/Projects/MedLands/WALES.htm).
[S1006] Cawley, Charles, "Foundation of Medieval Genealogy (Medieval Lands - Ireland)" (v4.0 Updated 13 October 2019) (https://fmg.ac/Projects/MedLands/IRELAND.htm).
[S2728] Baldwin, Stewart, "Medieval Genealogy Newsgroup: Eve of Leinster and Radnailt of Dublin" (soc.genealogy.medieval, July 28, 1996 (corrected August 21, 1996)) (https://groups.google.com/d/msg/soc.genealogy.medieval/hki_hNDwY8I/ULhLcNURHRIJ).
[S2730] Baldwin, Stewart, "Medieval Genealogy Newsgroup: Llywelyn ap Iorwerth Ancestor Table" (http://sites.rootsweb.com/~medieval/llywelyn.htm).
Family Note
Stewart Baldwin: 'No Irish source mentions ... the marriage of Radnailt to Cynan ap Iago. While it would be nice to have confirmation of these marriages in a more contemporary source, there does not seem to be any good reason to doubt them. The close connections of Gruffudd ap Cynan with Dublin are well documented.'

Stewart Baldwin: 'The name of the wife of Cynan ap Iago, her parentage, and her mother's parentage are known only from GaC (and sources dependant on GaC). Although reservations have sometimes been expressed regarding this information, enough of the data from the pedigrees of Radnaillt are verified in Irish sources that I am inclined to regard the information as genuine. For a recent discussion of this, see Seán Duffy, "Ostmen, Irish, and Welsh in the Eleventh Century", Peritia 9 (1995), 378-96.'