C62 Why not together

The reason why Xiao Chengzhen said that, was to warn Xiao Chengyi not to touch Mu Qianyu.

How could Xiao Chengyi not know what he was thinking?

After he had investigated Mu Qianyu's identity, he confirmed that he did not have any concerns, and wanted to bring Mu Qianyu into the Crown Prince Mansion.

He had been brothers for many years, and knew Xiao Chengzhen's personality very well