As King Henry VI's Uterine brothers Jasper and Edmund Tudor were also on very good terms with Richard Duke of York, even this good that both brothers were likely to be arrested for treason when they jointed York to London in January 1454 during King Henry VI's insanity. They even supported York at the council meeting when he received protectorship during the King's illness and not even the 1st Battle of St. Albans seemed to have changed their support to York.
...If Jasper was being pounded,
he’d [=William] pound through a thousand men.
The nobleman’s full of sincerity
(that will serve him well);
Gwilym [=William] is true and skilled
for one God before everything else,
also for the Crown, kindly eagle,
and above for the earl of Pembroke and his men.
Unfortunately Edmund would not be able to demonstrate more of his abilities in Wales, for he died at Carmarthen on 1 November 1456. Although suggested is the plague for a possible cause of death, an ample possibility, although there is no exact proof, is that Edmund’s sudden death so soon after the events of that summer, which was clearly a great shock and gives inevitable suspicion of violence or neglect during his imprisonment, is that Edmund suffered from wounds caused by opposing the force led by agents of the Duke of York.
Attempts to condemn the Deveraux-Herbert upheavals happened on 15 February 1457 at a Great Council, which opened at Coventry and closed some time before 14 March. Unfortunately there are no contemporary accounts of this council that survives but there is still the preface of 1459's act of attainder of the Duke and his followers. According to the preamble, the chancellor made divers rehearsals to the Duke of York which the Duke of Buckingham, on behalf of all the lords present, stated that the Duke of York could only lean on the King’s grace. Going on demanding York should be punished, should there be any repeat, but the preamble does not say of what. The document of the indictments makes no direct accusations to York which makes it difficult to directly blame him for Edmund’s death, even though Herbert and Devereux had to appear before the oyer and terminer sitting at Hereford from 2 to 7 April. For Herbert and Devereux the legal process went on for a few months and at the end it is difficult to see why King Henry responded to these men like he did, Herbert received a general pardon but Devereux was imprisoned and York received different modest gestures of reconciliations.