If Marrying a Chinese Woman can Her Children Come With Her To USA

Hello,

Question, If an American Man Marries a Woman From China who has a child who is 16 years old can the child come to the USA With The Mother ?

Is there a site to look at the rules ? The Mother says that if the child is older than 16 the child can not come to the USA with the Mother.

Please Help With Good Qualified Answers

Thank You