According to the 14th Amendment, anyone born in the US is automatically a citizen. What has happened many times is that lawyers acting in the name of this new citizen petitions for admission of his parents and the rest of his family. From reports that I've read, this is a pretty common practice. Current immigration law gives preference to citizens petitioning for admission of family members.

When my wife and I got married, she was a Filipino citizen here on a student visa. When we applied for her "green card" (which isn't green, BTW), we had too sign paperwork saying that if at any time we had to apply for government assistance, her application would be rejected and she could be deported. Back in 1983, immigrants were expected not to be burdens on the taxpayers.

Since then, it appears the system has changed radically so that new arrivals seem to automatically qualify for all sorts of public assistance. While I'm a big supporter of legal immigration, I'm opposed to them being allowed to stay if they are burdens on the taxpayers. There were elderly immigrants who immediately qualified for Social Security SSI payments even though they never paid a dime into the system. They were also eligible for food stamps and medical coupons. That's just plain wrong. No one should be entitled to money just because they made it into the US (or were born here, for that matter). The law has changed a couple times so new arrivals may no longer be eligible.