@nomas
In relation to your query about what laws promote the idea that you are responsible for the children in your house more than any children you make. This is how CMS works.
https://www.gov.uk/how-child-maintenance-is-worked-out
Step 4 - other children
The Child Maintenance Service will take into account the number of children the paying parent has to pay child maintenance for. This includes any other children living with them and any arrangements that have been made directly for other children.
www.gingerbread.org.uk/find-information/money/child-maintenance/using-cms/
Simon and Lucy are separated. They have 2 children, Evie and Ruby, who live with Lucy. Simon now lives with Jane and her 4 children. Lucy applies to the CMS for child maintenance.
Simon’s gross weekly earnings are £207.55 wages and some Working Tax Credits. Working Tax Credits aren’t counted as income.
Stage 1: Simon’s total weekly income is £207.55. This is reduced by 16% because he has 4 children living with him.
£207.55 x 16% = £33.21
£207.55 – £33.21 = £174.34
Stage 2: The maintenance due for 2 children is 16%.
£174.34 x 16% = £27.89
This is rounded to the nearest pound, so Simon pays Lucy £28 a week.
So as I was saying, the Government believe that Lucy can simply find a man who may or may not have children, but either way, will financially support her children in their shared home like Jane found Simon to do that in her home and family. It is set up this way purposely.