In order to petition the Department of Homeland Security to bring an alien to the United States with an immigrant visa, you have to first meet one of several conditions. First, you have to either be a citizen or a legal permanent resident of the United States. (I suppose a business could also petition for a worker of extraordinary ability, too).
Second, you have to with have a blood relationship with the alien or be married to them. If you are married to the alien, the alien's children, even if they aren't your own, could come with them.
You obtain form I-130, fill it out and follow the instructions that you can get on line.
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