Hengist Agnew, later Earl of Loghaire is a totally different person than Lochiel which may be entirely due to his mother's fondness (the countess of Loghaire) for him.
Hengist knows what he is worth and acts upon it. He dislikes of course his brother's homosexuality, in those days (1809 etc.) there is no understanding for such behavior, you were just deviant. As he does not expect ever to become Earl he chooses for a career in the army. Hengist is not born with a title as his father only obtains the earldom when Hengist is already born.
Yet Hengist is fed up with army life when he guides Wellington into giving him a leave for three months.
When he comes back in London to notice that his homosexual brother has married his adolescence sweetheart, he decides to do what it takes at the time. He faces enormous difficulties, but does the right thing at the right time, even if things can be called wrong from other points of view.
In the rest of the series he is always the helping protective earl which makes him a great person to love. If you ask me who my favorite is, I must admit it is Hengist, even if he has to break the law a few times to put things straight for himself and his family.