Why not? the people with the children sponser those people at old age, as they put money into there education feeding and what not, while the childless people did not, and yet they will benefit from the taxes thse children will pay too at old age, in fact if you don't do that the parents sponser the childrenless.But there is no way people who decide not to have kids would have to pay extra taxes as the person i quoted claimed.
There is a golden number of children per family that is 2.3 or 2-3 and that is what we should want people to have, not more nor less. our way to encourge that is economical and it is a just way to be frank.