Looking for an OG

Hello, I'm searching for this OG transmigration manhwa, it's one of the first of its kind. Romance, genre. A black haired girl is transported to another world, the ml has blonde hair and is the emperor, it has a lot of substance oh and in the end they have two daughters one becomes the empress. I know it sounds generic but what makes it stand out is it's one of the first of it's kind! Tysn