If the couple involved don't meet any of the three basic requirements in the Marriage Law the marriage is deemed invalid:

 

1. Both parties are willing to get married to each other.

 

2. Both parties are of legal marrying age: Male over 22 years old, female over 20 years old.

 

3. It's a monogamous marriage, neither party is already married.

 

(Shanghai.gov.cn October 17, 2006)