I Accidentally Saved the Male Lead's Brother

I woke up in the body of Charlotte Rania, an extra that was not even mentioned in the novel I had read. Because of that, I had thought that the cut-throat social world and politics were the worst I would have to deal with, but then I accidentally met a small child in the forest and saved him. Turns out the little boy is Theo, the younger brother of the male lead who died at the age of three! "I'm going to live with you!" When the little kid made a fuss that he wouldn't go home, the male lead Carlyle Heinst, who was originally supposed to be in a contract marriage turned true love with the female lead, offers Charlotte this exact contract marriage... Can I kiss my peaceful life as an extra goodbye now?! (Source: It Book, translated)