Legally speaking, there is no such obligation, unless the child's parents die and change guardians, parents will have this obligation to bring up the child. If you are not the guardian you don't have to. However, China's national conditions are such that parents have sacrificed much, much more for their children, for them, the child has to go to work and work, already very tired, parents for the child to work a little more, take the child.
So with or without children, the law does not provide, just parents are willing to take, willing to worry for the children only. This is the great thing about Chinese parents.