Shirobuta Kizoku desu ga Zense no Kioku ga Haeta node Hiyoko na Otouto Sodatemasu

The series follows Ageha, who is born into the world as the disliked son of a corrupt count. Ageha possesses all of the knowledge of his previous life, and learns that his half-brother Regulus will eventually attempt to kill him and take his title. Even with this awareness, Ageha decides to use all of the skills from his past life to raise his little brother.