The Squire's eldest son and heir to Hamley Hall, Osborne, is the apple of his eye. He grew up assured of his parents' adoration. And, since he is literary and writes poetry, they think that he is brilliant. They brag about him and shower him with attention- nothing is too good for their gifted son. When Osborne goes off to university, they are sure that he will perform brilliantly and come out at the top of his class. Indeed, they're banking on his landing a brilliant career. When he actually does quite poorly, they are shocked and disappointed, especially when it turns out that he has, in addition to his school fees, run up enormous amounts of debt. However, it is not so much his disappointment at his poor grades which causes the Squire's anger as it is his shattered illusions about his son, who seems to him to have repaid their love and indulgence with extravagance, ingratitude, and insolence. And of course, Osborne handles the situation all wrong... the squire is the type of quick tempered person who explodes in anger and then gets over it. But Osborne, wishing to avoid confrontation for a number of reasons, refuses to explain himself and his actions in any way. Had he done so, the Squire would have gotten angry and then settled down. Instead, he is left to conjecture, imagining the worst about Osborne's refusal to say what he's done with all the money, causing his bottled-up anger to fester and grow. Then, when Osborne dies suddenly, the Squire is devastated that his son died with their quarrel unresolved, not knowing how much he loved him. And when the reasons behind Osborne's actions are revealed, he is tortured by the knowledge that his son was afraid to tell him the truth.
Of course, the problem with being constantly told that you're destined for greatness is that it can make you lazy and entitled. After all, if fame and fortune is your destiny, you shouldn't have to work very hard for it. Not that it appears that Osborne didn't try at school, but having had everything come easily to him for his entire life, he expected that scholarly success and honour would come just as easily. And it didn't. The same attitude is responsible for the entire mess with Aimee. Osborne meets and falls in love with a poor French girl, and marries her. Now, I certainly think that class and nationality should play no role in marriage, but Osborne behaves like an imbecile. For him, a young man with no money and no job- and no job prospects- who is dependent on his father's support, to marry a girl who is guaranteed to make his father furious, is problematic, to say the least. But again we see Osborne's rationale: everything has always worked out for him, so no doubt this will just work out, too, no matter how rash his actions. Now, don't misunderstand me, I'm not saying that he shouldn't have married Aimee, but that he should have secured a means of supporting a wife and family before he did. And what was the rush? Aimee wasn't in dire circumstances- she had a respectable job. They rush headlong into it, though, because it's what Osborne wants, and he has always been given what he wants. And then he's confronted by real life, where everything isn't handed to you on a platter just because you're special. Even then, he tries to avoid negative consequences by hiding Aimee and his son away at a remote farmhouse, while still living off his father's- and Roger's- money. He should have faced up to his responsibilities, been honest with his father, and open and above board about his marriage. That's called being an adult, and if you aren't one, you've got no business being married.
Osborne's relationship with Roger is also heartwarming. The two brothers, despite the inequality of their parents' treatment of them, are always close. Though he keeps his marriage a secret from everyone else, Osborne takes his brother into his confidence. And just as Roger never resents Osborne for being the favourite, so Osborne never resents Roger for his scholastic achievements. On the contrary, he is very proud of his brother, and says so, despite it highlighting his own lack of success.
It's quite likely that, given time, Osborne would have pulled himself together and become a responsible family man and son. He is, at the core, a good and honest person who has a loving wife and family. I think he would have manned up and faced his father with the truth about his marriage. And, stripped of his illusions about easy success, he no doubt would have applied himself to learning what he needed to know about running Hamley, becoming a responsible landowner even if it wasn't the literary career he dreamed of having. Unfortunately, his failing health makes this impossible. As he becomes weaker, Osborne becomes even less willing to confide in his father, feeling physically unable to deal with the Squire's inevitable anger. And his increasing frailty also makes it difficult for him to ride about the estate, or engage in any physical exertions, so he is unable to learn about Hamley and its management, even if he wanted to. When he dies, the tragedy is not only that he was so young, but that his life was cut short just at the time when he was becoming humble enough, and mature enough, to turn his life around and become a responsible husband and father, a dutiful son, and a productive member of society.