Complex sentence: In Winterfell, Ramsay Bolton's status as heir to the North is threatened by Sansa's escape, prompting him to kill Roose and Walda Bolton and his new-born half-brother to secure his position.
Split into simpler sentences: In Winterfell, Ramsay Bolton's status in the North is threatened by Sansa's escape. He kills Roose and Walda Bolton and his new-born half-brother to secure his position.