Loreon Casterly is almost like the forgotten son of Lord Tywon Casterly. He's the youngest and is neglected by Tywon, Tywon feels resentment to his youngest son - after Loreon's mother died giving birth to him.
Right from the start, Loreon appears to trump his father and brother. He appears at the end of the joust with men so that more buzz can be created for his arrival than Jamie's win, to up jump his father. Throughout the story Loreon is trying to get one over his father, he helps Ignis against his father by discovering his plot for the double marriage through the Grand Maester. He's being pushed against his family, his father doesn't include him in his marriage plans - he has not interest in planning his marriage - and his cousin, Jayna Casterly, harasses him. The only one that treats Loreon normally is his brother Jamie Casterly AKA The Kingslayer, but Jamie still holds ties to Jayna and Lord Tywon and doesn't commit like Loreon already has. Even then, Jamie is sent out to The Hunter's Gift and even when he is captured, his bad reputation and (for lack of better word karma) means that no one will help Loreon rescue him.
However there is something sinister hiding behind Loreon Casterly. We know that he is widowed, and there's something fishy about it. Loreon says he was too hard on his wife, and whenever someone brings up his former wife there are some tensions that arise from Loreon. Something happened to his wife that we are not being told. He has a dark side that we see in his one and only chapter, where he verbally abuses Jayna Casterly. With Jamie as well he's very self-loathing and almost suicidal, where he tells Jamie that he'll hang himself soon. It seems to be tied into his backstory that we don't know too much about.
Loreon seems on a quest as well to get something from Ignis. To get Ashara from him, we think that Loreon is trying to get a new wife and actually he says he does because he wants to leave everything behind and just live with his new wife. But he is being continually rejected, Ignis keeps reaffirming his promises to Loreon but he never caches them in - he heaps up favours that go unrequited for the moment.
Loreon, for now, is stable and working on a plan - he has feeling of self-hatred however he can control them, as they don't appear within his chapters with Ignis. We'll have to see if he can continue to hide his past.