How come some ppl receive more welfare than others?

My mom had my brother me more than ten years ago. As a single mother she started receiving welfare money and food stamps for both of us. In the 90s i believe there was a law about welfare stating that if a person had two kids on welfare the future kids couldnt recieve that help anymore. My mom had three kids after us n only recieves help for two. But i think she gets food stamps for all and just money for two im not sure. Im now 18 n she doesnt get any money 4 me only foodstamps i think. Well she now gets about 400 or less money for my brother with me it was like 500. Foodstamps is like 500. The thing is i see some friends that have like four or five siblings n get about 800 or more in money and i dnt get it because arent they supposed to get help only for two kids? Theres also a young couple who had a baby last year n get about 300 n theyre about to have another baby. In total for the two theyll get like 600. If they have more kids in the future will they get more money for them? I hope not bcause the law.