Having US citizen children doesn't change your status. Your kids won't be able to petition for you until they are 21 years old.

IMHO is correct, however you have been in the states five years at least is there a reason as to why you have not applied to become a citizen? This is a option that you have.You can go online to U.S. Immigration and fill out the form N-400 U.S Citizenship Application.

Thanks to IMHO and tomturkey. I have been on a student visa and haven't started the green card application yet. In case I couldn't continue to be on a student visa or a working visa, can I stay in the US legally for the reason that I am the legal guardian of US citizen children?

Thank you Mickycardo! Yoy can fill out an application for citizenship , however you cannot stay in the US because you are the legal guardian of your children. I wish that were possible for you.

Thank you very much, tomturkey. I hope I can extend the stay by getting another non-immigrant visa. Meanwhile, I will try to apply for green card. Thank you again. By the way, may I apply for citizenship using the reason of being a guardian?

You do not need to apply for citizenship by stating your the guardian of your children, anyone can apply for citizenship. Again thank you, I am sure everything is going to work out for you.

Thanks a lot, tomturkey.

Your welcome and if ever you need additional information let me know, thanks!