Wakeari Youjo, Tensei shita Koto ni Kizuita no wa, Shuraban ni Sougu shita Toki.

One day, Tori a 4 year old who lives in the poor countryside, is visited by a beautiful noblewoman who tells her that she is a descendant of the Middleton family, a family of counts. Tori is suddenly brought to the Earl's house, where she is treated roughly by the cold-hearted Earl and his older brothers. However, Tori wins them over with the cuteness of her youth...! Before long, Leonardo, the first prince of a neighboring country, asks her to marry him, saying that he is the man of her dreams...! (Source: MangaPlaza)