*Helen (Elen) verch Llewelyn
born about 1230/34 Wales

father:
*Llewelyn "Mawr" "The Great" ap Iorwerth King of Gwynedd & Powys
born 1173 Aberffraw Castle, Caernarvonshire, Wales
died 11 April 1240 Aberconwy, Arllechwedd Isaf, Caernarvonshire, Wales

mother:
*Joan Princess of England
born about 1188 London, Middlesex, England
died February 1237 Aberconwy,Arllechwedd Isaf,Caernarvonshire,Wales
buried Llan-faes,Dindaethwy,Anglesey,Wales
married after 16 April 1205

siblings:
*Dafydd ap Llywelyn born about 1209 Caernarvonshire, Wales died March 1246
*Angharad verch Llywelyn born about 1212 Caernarvonshire, Wales
3 other sisters

spouse:
*Donald 6th Earl of Mar
born about 1240 Kildrummy, Aberdeenshire, Scotland
died after 25 July 1297

children:
Margaret de Mar born about 1270 Mar, Aberdeenshire, Scotland died before 24 July 1326
Garnait Earl of Mar born about 1272 Kildrummy Castle, Kildrummy, Aberdeenshire, Scotland
died before September 1305
Duncan of Mar born about 1274 Kildrummy Castle, Kildrummy, Aberdeenshire, Scotland
Alexander of Mar born about 1276 Kildrummy Castle, Kildrummy, Aberdeenshire, Scotland
*Isabella (Matilda) of Mar born about 1278 Kildrummy Castle, Kildrummy, Aberdeenshire, Scotland
died about 1320
Mary of Mar born about 1280 Kildrummy Castle, Kildrummy, Aberdeenshire, Scotland

biographical and/or anecdotal:

notes or source:
LDS
ancestry.com
"Biographical Encyclopedia of the Kings & Queens of Great Britain" by Mike Ashley