Yuuhi's manga / #Child MC(2)

Ch. 21 - The MC and the Duke are spending all their their time together to seem like actually father and daughter in front of the emperor. The Prince came to visit.

Ch. 73 - The White Haired Boy’s mom is displeased that he went to MC’s 10th birthday party so, she took him to her underground dungeon where he saw all his “siblings” in a cage. Ch. 21 - The Crown Prince, MC’s step cousin, is back. She wanted to have a good relationship with him but he stood her up at her tea party. Apparently he is supposed to die soon from a carriage incident. After he dies, the white haired kid becomes the crown prince. And he too also died at age 15 (currently 12).