The compound surname is the basic surname, which is as stable and legal as the single surname. Two singles can only form a double surname, not a compound surname. For example, the combination of Guo surname and Li surname can only form two different double surnames, Li Guo or LiGuo, but not two new compound surnames; In other words, the inheritance of compound surnames is legal. Guo He's children can be surnamed Guo or Li, which is the legal surname. Guo's or Li's compound surname is temporary and illegal, and the legal approver can only be the original Guo or Li. In addition, double surnames are more popular in Hong Kong.
I am on a business trip now. Please explain by asking questions if necessary. I'll send you the national standard of surname later.