So, will Robert’s Rebellion be in House of the Dragon? Robert Baratheon led a war against the Targaryens’ rule decades before the events of Game of Thrones. During that time, he sought out Rhaegar Targaryen, who he believed kidnapped Lyanna Stark, who Robert was arranged to marry.
Robert got it all wrong, however, and Lyanna loved Rhaegar, which only made things worse.
Source: https://www.distractify.com/p/is-roberts-rebellion-in-house-of-the-dragon