Sadb Ni Faelain
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Family
About
Sadb Ni Faelain was of the Ui Faelain, one of the three ruling septs of the Ui Dunlainge, the dynasty that held the over-kingship of Leinster in rotation for three centuries from their seat at Naas. She was the first wife of Diarmait Mac Murchada, King of Leinster, and the mother of Orlaith, who married Donal Mor O'Brien. Through her this family's line runs up the Leinster kings to the fifth century, the deepest reach in the whole tree.
Research notes
✓ per the DICTIONARY OF IRISH BIOGRAPHY (Aynsley's check, 23 Jul 2026): SADB NI FAELAIN, of the UI FAELAIN (a ruling dynasty of north Leinster, the Ui Dunlainge kings of the Liffey plain - note-only, extendable); 1ST WIFE of Diarmait MacMurchada, King of Leinster; identified as the mother of ORLACAN (our line, m. Donal Mor O'Brien) - which makes Orlacan the HALF-sister of Aoife. GRADE ~ on this maternity: the DIB prefers Sadb, O'Hart gave 'dau. of O'Moore of Leix', and some trees make Orlacan a full sister of Aoife (mother Mor Ni Thuathail). Entered as mother per the strongest source (DIB). Direct ancestress (grade ~). Added 23 Jul 2026.