House Baratheon is the ruling royal house when "Game of Thrones" begins, but their role is less central in "House of the Dragon." The house's origins are actually depicted in the book "Fire & Blood." The book covers several generations of Targaryen rule, starting with the conquest of Westeros by Aegon I. House Baratheon is founded by Orys Baratheon, one of Aegon I's generals, when he marries the last heiress of a conquered house. The houses remain closely tied together; Princess Rhaenys's mother is Lady Jocelyn Baratheon, whose mother is the Dowager Queen Alyssa Velaryon.
Boremund Baratheon (who's Jocelyn's brother) is seen in the first episode of "House of the Dragon" also pledging his support to Rhaenyra. He appears again in episode four when Rhaenyra's tour of Westeros takes her to meet the eligible suitors of the Stormlands in Storm's End. But by the 10th and final episode of the season, he's been replaced by his son Borros, who doesn't side with Rhaenyra.
