They will also be able to apply for you to become citizens when they turn 21 via an Alien Relative Petition. They will likely not pay much tax between now and

They will also be able to apply for you to become citizens when they turn 21 via an Alien Relative Petition. They will likely not pay much tax between now and then so the cost of the opportunity (if you would ever consider living in the U.S. permanently) is minimal.