At a panel discussion, legislator Luo Liangquan said the amendment draft to the family planning law is of great significance to the nation in improving demographic structure and safeguarding the harmony and happiness of families, state-run Xinhua news agency reported.
The timing to amendment the family planning law was also hailed by other legislators, including Liu Zhenqi, who said the new rule was necessary to encourage more couples in the nation to have two children amid rising costs of bringing up an additional kid.
The draft came after the Communist Party of China Central Committee decided in October to give the go ahead for the universal two-child rule, which will replace the decades-long "one couple, one child" policy.
NPC routinely approves CPC decisions.
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China's family planning policy was first introduced in the 1970s to rein in the surging population.
For decades, most urban couples were limited to one child while rural couples were allowed to have two children if the first child was a girl.
The population of senior citizens has been increasing rapidly in recent years, while the labour force is contracting.
China has a population of 1.3 billion, the largest of any country in the world. The number of people aged 60 or over in China reached 212 million at the end of 2014, accounting for 15.5 per cent of the country's population, with the number of disabled elderly people approaching 40 million.
The new rule in the draft is expected to further stabilise China's total fertility rate (TFR) or the number of children that would be born to a woman of child-bearing age, which stood at 1.65 per cent in 2014. The reading dipped to about 1.21 per cent in 2012.
However, according to recent official surveys not many of 100 million couples who could benefit from the new policy were interested to have a second child in view of growing costs of bringing up an additional kid.