Chief Sean O'Cahan
This Sean O'Cathain, son of Aibhne, took over the chieftaincy of the O'Cathain Sept from his murdered second cousin. Sean O'Cathain had a difficult time from the beginning of his reign, with his son being captured by Conn O'Neill in 1489. In 1490 Sean O'Cathain was himself captured by a scottish vessel from Inveraray. Liberated the following year, he showed his quality for decisive action by returning and rescuing his cattle from the sons of Manus O'Cathain before anyone in his own territory even knew of his liberation from the Scots.
Sean O'Cathain took an active part in the fued between the O'Neill claimance to the O'Neill title. For in the year 1492, Sean O'Cathain created Henry O'Neill as the O'Neillin defiance of his elder brother, Donnell O'Neill who was already appointed "the O'Neill".
Natural calamities shadowed Sean's chieftaincy for in 1496 the Annuals of Ulster relate that there was great inclemency of weather. Husbandry was hindered, and there were enormous losses of cattle resulting in serious famine in O'cathain territory. Sean died in 1498 and was succeeded by his brother Thomas O'Cathain.