Shirohiyo - Reincarnated as a Neglected Noble: Raising My Baby Brother With Memories From My Past Life Shirobuta Kizoku desu ga Zense no Kioku ga Haeta node Hiyoko na Otouto Sodatemasu

In a world where Western and Asian cultures mix together, the only son of Count Kikunoi from the Kiryuu Empire, is Ageha. His life was already over at the age of 5. He, who was born in a corner of the country, has zero allies or useful skills in addition to being overweight. What's more, it seems that his brother Regulus, who suddenly appeared on his life and was presented for the Count as his brother, will kill him in the future for his right to succeed... His only weapons, are the abilities of "cooking and sewing," that he suddenly acquired along with the memories of his previous Japanese life. In the midst of all this, Ageha ends up raising his younger brother, but... "My brother is super cute?" And before he knows it, he becomes a full-blown doting older brother?! Making handmade educational toys for his cute little brother and delicious chawanmushi (steamed egg custard)... With the help of his previous life's skills and my power as a housekeeper, he's able to improve the rough life of the people living in his territory. A fantasy of two young brothers managing their territory, where a single step gets even the gods involved in changing their country! (Source: Shousetsuka ni Narou, translated)