More than 100 parents with children who are gay or lesbian have written to the National People's Congress calling for the legalisation of same-sex marriage.
"We're appealing to NPC deputies to take notice of calls from 120 million parents of gays and lesbians for a revision of the Marriage Law in order to grant our children equal rights to marriage," they said in an open letter.
The NPC will convene its annual session in Beijing on Tuesday.
Homosexual relationships are not recognised under mainland law, which means that people involved in them face discrimination in matters such as hospital visits, inheritance, adoptions and home purchases.
One signatory, the mother of a 23-year-old man from Shenzhen, said she was worried about her only son's future because legal inequality would deprive him of a decent life, having a partner, a family and the chance of adopting a child.
She said she had learned to come to terms with her son's homosexuality after he came out to her four years ago and considered his well-being more important than the fact she could never be a grandmother.
Hu Zhijun , a gay rights activist from Parents, Families & Friends of Lesbians China, said the parents issued the open letter after receiving very few responses from NPC deputies they tried to reach through letters and social media sites since January.
He said the law was flawed because mainland homosexuals could marry a heterosexual partner legally, although they were not in a loving relationship. This gave rise to the phenomenon of "gay wives" and "gay husbands", heterosexual women and men who unknowingly marry homosexuals seeking to use such marriages to conceal their sexuality.
Dr Lucetta Kam Yip-lo, a gender and sexuality specialist from Hong Kong Baptist University, said the mainland might be more likely to legalise same-sex marriages than Hong Kong, where Christian beliefs exerted a strong political influence.
"Most pressure on LGBT (lesbian, gay, bisexual and transgender) individuals to conform to heterosexual norms does not come from the governments but their families," she said.
A mother from Fuzhou , Fujian , who has a 26-year old gay son, said she was devastated when he told her about his sexuality two years ago and felt even worse when she could not turn to friends and relatives for help due to the stigma involved.
But she said she had decided to take up the fight for gay marriage due to widespread hostility towards people like her son, who was forced to drop out of middle school due to bullying.
"We're not asking for special treatment for my son, but wanting him to be treated equally because he is as filial and talented as anyone else," she said.
Additional reporting by Joanna Chiu