Little Zhanzhan's Wish

Song Yu Han never viewed the Song Family as his. It was just the family that abducted him and took his mother's life.

However, he was young at that time. His hands couldn't even reach out to destroy them, much less damage Song Yichen's arrogance. Hence, he plotted a plan to lower his guard by acting as if he had been finally enlightened that he could only stand beside his grandfather. 

That's right. All along, Song Yu Han knew that his grandfather never truly saw him as his grandson. He probably grew some bit of affection over the years, but at the beginning, his only purpose and goal why he had agreed to his mother's condition was for Song Yu Han to see him as his savior, someone who could save him and protect him.