I'll Live a Long Life to Dote on My Favorite Stepbrother!

Alba has been reincarnated as the son of an impoverished noble family. When his mother remarried into a dukedom, he was introduced to his stepbrother, Orsis, his "favorite person" from his previous life. “Does this mean my favorite is now my stepbrother?” he thought joyfully, But he suddenly remembers that he was the r…