Petition No child benefit for being a married couple??????

Basically it looks like if you are an honest married couple with children,mortgage and work to live you get punished,if you are a single mother with children and you have a boyfriend that works and is not on the birth certificate but can still live with you for a few days a week,you get all kinds of rewards and the boyfriend doesnt even have to declare he knows the single mother!!!!.
so they both bring in more money and get rewards than a married couple who work or usually one works and the other has to stay at home to look after there children.
If the govermant are trying to encourage family's to live together so there is a mother/father figure
,get peolple into work and get off benefits and raise there children so they know the meaning of a honest days work why do they not see this loophole in the system.Is it not hard to see that if you are a single mother with a boyfriend who works(but does not excist)you get rewarded.