How do Stephan and Jeremy die?

Jeremy Poldark is Ross and Demelza's second child. In The Twisted Sword he has reached the age of manhood, happily married to Cuby and with a baby on the way. Like so many men of his generation he's become caught up in the Napoleonic Wars currently ravaging the European continent. Jeremy's stationed near Brussels, the capital of modern-day Belgium. He proves himself to be a very brave, skillful soldier and is subsequently promoted to Captain. With exemplary courage, he leads his men into battle, but tragically it proves to be his last. Jeremy is shot twice and dies in the arms of his father.
Stephen Carrington's off on his adventures too. Sadly for him, they end up the same way as Jeremy's. To help solve his perennial financial troubles he captures a ship. It's a prize catch indeed, and Stephen makes an absolute bundle out of it. But his new-found wealth goes to Stephen's swelled head, and he starts acting like a king. As a newly-minted man of substance, he feels himself entitled to better things. He buys a magnificent horse that he feels is an appropriate reflection of his elevated station in life.
Yet as Stephen soon discovers, pride comes before a fall—in this case, quite literally. He tries to impress the comely Harriet Warleggan with his skills as a horseman and foolishly challenges her to see whose horse is best. Unfortunately for Stephen, his horse comes off worst, and he comes off the horse. Thrown from his steed as it fails to negotiate a particularly difficult jump, Stephen breaks his neck. How the mighty have fallen.