Background
A son of Melaghlin Ó Maolalaidh, Seán was to be the last Chief of the Name to live in the family"s original homeland. Sometime after his election as chief in 1419, and by 1445, he, his clan and followers were expelled from the area by the Mac Hubert Burkes (Annals of Connacht - 143610 Seonacc son of Hugacc Burke died).
Career
The Ó Maolalaidhs (Lally, Mullally) were, with the Ó Nechtains (Naughton), one of the two leading septs of Máenmaige in western Uí Maine. There is some evidence to suggest that they were not of the Uí Maine dynasty, but an indigenous people conquored by the latter in the 7th or 8th century. Seán led the family to Tuam, where he leased eighteen townlands from Baron Athenry.
One of the townlands was Tullaghnadalaigh (Tullynadaly), some four miles outside the town and thirty miles from Máenmaige.
Seán died in 1480, having been chief for sixty-one years, and was buried at Kilbannin. Tullynadaly was to remain the seat of the senior line of the family until their seizure in the 1690s.
Many Mulallys and Lallys are still found in the Tuam area. Some of Seán"s notable descendants included Amhlaoibh Ó Maolalaidh, floor
1333, father of Donal mac Amhlaoibh, k.
1397, father of Melaghlin mac Donal, floor c. 1400, father of Seán Ó Maolalaidh, floor 1419-1480, father of Diarmaid Ó Maolalaidh, daughter
1517, father of Melaghlin mac Diarmaid, floor
1541, father of Seán mac Melaghlin, floor 1544, father of Diarmaid Ó Maolalaidh, daughter
1596, claimed, falsely, by William Hawkins, Ulster King of Arms, and principal Herald, to be the father of Issac. lieutenant was discovered in 1902 <ref>The September of O"Maolale or Lally of Hy-Maine" by J Martyn, in: Galway Archaeological and Historical Society pp198-211 see: </ref><ref>Alumni dublinenses: a register of the students, graduates, professors and provosts of Trinity college in the University of Dublin (1593-1860) See: </ref><ref>Blake, Martin J., Notes on the Persons Named in the Obituary Book of the Franciscan Abbey at Galway, J.G.A.H.S., Volume
7, Number. 1, 1911, p. Issac Ó Maolalaidh, daughter
12 May 1621, father of James Ó Mullally, daughter 5 September 1676, father of Thomas Mullally, died before June 1677, father Colonel James Lally, daughter 1691, brother of, father of Thomas Arthur, comte de Lally, baron de Tollendal (1702-1766), father of Trophime-Gérard, marquis de Lally-Tollendal (1751-1830), second cousin of Thomas Lally, Senior, of Tuam, floor
1817, son of James Lally of Milltown.