YANBU.
Most people do receive some sort of help financially with bringing up their kids, eg education, health, tax credits, BUT by working to support their children, they are contributing to the overall cost, and to my mind, it doesnt matter how big or small the contribution in terms of money into the system, but it does matter that they feel that it is right to work and contribute.
There is a big difference between that and people having one child after another without ever having contributed to the benefits system that supports them.
Also, you may say that these children who are being born to such parents are the next generation of workers - not bloody likely! with the example which is set for them by their parents, that work is something that other people do, its unlikely that such children will ever be anything but a drain on the country's resources. I'm sure there are exceptions to this rule, and much credit to anyone who manages to break out of the mould of their parents and gets a job, but it is really the exception to the rule, as I know many families like the one OP is describing, and they are now on their 4th generation, and none of them have ever done a days work in their lives, and this is definately by choice, as I, living in the same area, in the same job market, have never been out of work for more than a couple of weeks.
I should just mention here that I have no problem with people on benefits because they have no choice - illness, disability, lone parent unable to work, that is one thing, but they are most definately in the minority where I live.