Towards the end of the 15th century, Edmund, son and heir of Thomas, was caught up in the aftermath of the wars of the Roses. The Geraldines strongly supported the House of York against that of Lancaster and regarded the defeat and death of Richard III at the battle of Bosworth Field in Aug 1485 as an unmitigated disaster. They refused to accept the Tudor king, and for the following 12 years their policy was aimed at a restoration of the House of York. Thus the pretender, Lambert Simnel, was warmly welcomed in Dublin in March 1487 and crowned Edward VI. He next attempted to impose his rule on England. Despite the assistance of strong Geraldine forces and German mercenaries, the attempt ended in disaster at the battle of Stoke in June 1487. Yorkist hopes were raised again in 1491 when a second pretender, Perkin Warbeck, landed in Cork. He received considerable support throughout Munster. Edmond, the knight of Glin, was one of his leading supporters. The knight led his followers to Waterford from where Maurice, 9th Earl of Desmond, had called all the Gerladine nobles and their followers to him. However the expedition was a failure. Henry VII was furious at the repeated involvement of the Geraldines in rebellion, but he was powerless to subdue them. So he pardoned them and in this royal pardon, which was issued at Lewes on 26 Aug 1496, Edmund, Knight of Glin "Edmundo Milite de Walley" was listed. Edmund was interested in the ecclesiastical life of the time. He and his wife, Honora MacMahon, widow of a FitzGibbon, were responsible for building the infirmary of the Franciscan Friary at Adare.19

The only son, had his title confirmed by Henry VII, and was pardoned by the King (tested by him at Lewis, 26 Aug 1496) for complicity in the rebellion of Perkin Warbeck.