The King remembered his brother and Hae So's child well. She looked exactly like her mother. But this planted doubts in his head : "Could this child be mine and Lady Hae's?" He had to know. Hence why he went to his brother's house. He wasn't so warmly greeted. Wang Jung kneeled before him :

"Your imperial Majesty, long time no see."

"My Brother, rise up please." And rise up he did.

"It's been a long time since we last saw each other, my imperial brother. What brings you here?"

"Your child. Last night, I couldn't sleep because I had a nagging feeling that she could be mine and Hae So's. Might I see her?"

"What gave you that idea? I can assure you she's mine and Lady Hae So's."

"I just want to see her once. If she's mine, then I'd make sure she gets her proper place in the palace."

Just then, the child in question appeared from nowhere, playing with a colored ball. His brother saw her first, attempted to hide her, but the King was faster, he went to her. As soon as he saw her, a feeling rose in him, he remembered the night Hae so and he made love. It was exactly 9 months ago till the day she married his brother. So, she was already pregnant with his child. He looked at her intently without speaking for a long time. She was her mother's spiting image, but she was maybe 10-12 years old? He sensed himself in her as well. This child was his, no doubt now. The first time he saw her, his brother quickly hid her from his sight. Now that he's got a closer look, he felt a connection between this little girl and himself. He was so elated, Hae Soo left him a legacy. His brother spoke to him first :

"I'm sorry she disrupted you, your imperial Majesty, I'll bring her inside."

"My Brother, don't attempt to hide my child from me. You knew from your first sight on her that she wasn't yours, yet you deliberatly hid my own flesh and blood from me,  I'm taking her to the palace."

"But Hae Soo didn't want her to live a life in the palace, she wanted her to lead a quiet and peaceful life."

"I don't care, but she's mine, I'm taking her to my palace to be raised as my beloved princess."

Thus, his imperial Majesty said to the little girl watching the 2 adults :

"Little girl, you're mine and the only woman I loved's flesh and blood. You can come with me to the palace to live as my beloved princess."

The child, innoncent and wide-eyed, followed him.

"You won't get away with this, my imperial brother, I'll take her back where she belongs, I've been raising her for 10 years."