Two plastics firms made the latest Forbes' top 50 listed family companies in China.

Janus (Dongguan) Precision Components Co. Ltd., majority-owned by the Wang Jiuquan family in Dongguan, Guangdong province, was ranked 21st. The company was founded in 2003 and launched an initial public offering in May 2010 at ChiNext, a Nasdaq-style growth enterprises board hosted by the Shenzhen Stock Exchange.

Janus makes precision electronics components and molds for leading OEMs including Samsung, Huawei and Haier. Samsung alone represents more than half of Janus' revenues.

Over the past three years, Janus has seen sales grow at a compounded annual rate of 69 percent and net profit 36 percent.

Also included in the list is auto compounder Shanghai PRET Composites Co. Ltd., coming in at 36th. The company was founded in 2007, went public in December 2009, and is majority-owned by the Zhou Wen family.

Sales grew 15 percent annually and net profit 64 percent for PRET in the past three years, reflecting the healthy demand of the booming Chinese auto industry.

According to the first "Chinese Family Business Survey" by Forbes China magazine, as of the end of June, a total of 305 family businesses are listed companies on the Shanghai and Shenzhen stock exchanges, accounting for 36 percent of the total number of listed private enterprises.

The survey shows that the listed family businesses beat listed state enterprises in terms of sales growth and profitability.

More than 60 percent of the polled entrepreneurs hope to have their businesses inherited by the second generation.