In the family portrait, the Canadian-born singer and actor is holding a baby girl, flanked by Chinese-born model Shu Pei Qin, his parents and his two older sisters. Behind them, party decorations spell "Alaia's 100".
After months of rumours that Chen is starting a family with Qin, the photo seemed to be proof, said Ming Pao Daily News on Tuesday.
The picture of the party was uploaded by Chen's friend with the message "100 days congrats", said the report, and a netizen immediately did the math, concluding that the singer's daughter was likely born on April 20, 2017.
Chen, 36, and Qin, 27, were first reported to be dating last year. Soon, there was talk that she had not finalised her divorce from Huayi Brothers Fashion Group chief executive Zhao Lei. Then, Chen made more headlines by attacking model Chiling Lin on Weibo and accusing her of blocking Qin's attempt to join the fashion reality show Hey Muse.
Months ago, he was rumoured to have gone to the United States to accompany Qin during the birth of their child. Apple Daily said he also bought a US$2.85-million (S$3.94-million) home in Los Angeles.
He has declined to confirm the rumours to the media.
But during his set at the Strawberry Music Festival in Xian, China last month, he could not seem to contain his happiness. He told the audience: "If I wasn't so crazy, would you remember me? If I got married and had a child, would you remember me?"
This story first appeared on The Straits Times on June 13, 2017.