Why did Henry marry his sister-in-law?

Henry VIII married his sister-in-law, Catherine Parr, primarily for political stability and to secure a male heir. After the deaths of his previous wives, he sought a companion who could also fulfill the role of a caretaker and help manage his court. Catherine was also a widow and had experience in managing royal affairs, making her a suitable match at the time. Additionally, their marriage reinforced alliances and ensured continuity in his reign.