Was he older than Richard?
If so, Richard's career would be significantly impaired. An older brother, no doubt well endowed with property and retainers of his own, well married to a wife well born and connected, defending the Queen Dowager and royal heirs, versus a younger brother with zero claim to the throne or any kind of regency/protectorate.
If Edmund survives, George probably stays reasonably loyal. There's no throne in it for him. Supposedly Edward and Edmund were close, which suggests that Edmund would be more loyal than George was in OTL. Warwick might behave differently too, if he couldn't pull George along on his rebellion. Would George even marry Warwick's daughter?
In order:
Edmund, George, Richard.
But would Edmund necessarily be loyal to his older brother? I think we have to address his career up to Edward IV's death (which may happen at a different time than OTL - Edmund as a loyal supporter would make a difference in Edward's reign) before addressing afterwards.
He was a younger brother of Edward IV of England and was killed at the battle of Wakefield along with his father. WI: He had lived, married and survived Edward IV. Could this possibly prevent Richard III's usurpation and even the Tudor succession?
He was a younger brother of Edward IV of England and was killed at the battle of Wakefield along with his father. WI: He had lived, married and survived Edward IV. Could this possibly prevent Richard III's usurpation and even the Tudor succession?