Bérnwyn is a Rohirrim princess who is the daughter of Helm Hammerhand and Éowyn Ethelfléd. She was the sister of Haleth, Háma, and Aelda. Married to a Rohirrim Warlord named Siric, she was the mother of Siri. Before the Long Winter came to pass, Bérnwyn was nearly killed by a group of Dunlendings until she was rescued by Siric. Bérnwyn fell in love with him and decided to remain in Snowbourn while her father was unaware that she was alive. Throughout their time, she became pregnant and gave birth to a daughter.