People's Republic of China (PRC)'s Constitution stipulates that the marriage partner must be a boy or a girl.

There is no provision in the constitution, but there is provision in the marriage law.

Marriage Law

Article 5 Marriage must be entirely voluntary, and neither party may force the other, and no third party may interfere.

Article 6 The age of marriage shall not be earlier than 22 for men and 20 for women. Late marriage and childbearing should be encouraged.

Article 7 Marriage is prohibited under any of the following circumstances:

(1) lineal blood relatives and collateral blood relatives within three generations;

(2) Suffering from diseases that are medically considered unsuitable for marriage.

Article 8 If both men and women want to get married, they must go to the marriage registration office for marriage registration in person. Those who meet the requirements of this law shall be registered and issued a marriage certificate. Getting a marriage certificate is tantamount to establishing a relationship between husband and wife. Those who have not registered for marriage shall re-register.