The story is set in the early years of the 19th century. The hero and heroine, brother and sister, are children of Sir Roland Lorraine, representative of a very ancient family. Hilary, while studying for the bar in London, falls in love with the daughter of a Kentish farmer, the sister of his fellow-pupil. He confesses his folly to his father, who at once buys for him a commission in a regiment of foot on service in Spain. The young man distinguishes himself at Badajos, and is on the high road to fame, when he falls under the spell of a Spanish countess, and forgets for a time his promise to the Kentish girl. Through the countess's treachery he loses ÂŁ50,000, military funds, with which he is entrusted, and leaves the army. Meantime his sister has been fighting a severe battle at homeâdefending herself against a plot to make her the wife of a drunken fellow named Chapman. Hilary comes home; Mabel, the Kentish girl, is sent for, and matters are serene with all but Alice on the day appointed for her wedding. When the hour for the ceremony approaches, she walks out and throws herself into the river, is carried a mile, rescued and resuscitated.

Question: How are the story's protagonists related?
Answer: they are brother and sister
Alternative answer: brother and sister