Yes Edmund Kean was an admirer of Aldridge. This is underlined in the play when Pierre said that Edmund cast Ira Aldridge over his own son.
Yes Charles Kean did play Iago to Aldridge's Othello in Belfast which is dealt with in the play when Charles says he was ill and unable to play there (to add to the dramatic tension of the scene) but he did not play opposite Ira at Covent Garden. Why not?
Always good to know all the facts before passing comment.