Did they enter the country with a B-2 visa and overstayed? If that's the case, it's probably too late to file for a change of status. You should consult with an experienced immigration attorney who can review their immigration histories and assess their options before filing anything.
[This answer is for general purposes only; it does not constitute advice and does not establish an attorney-client relationship.]
There's no magical answer except the truth but given the information you've provided there's more information needed. I agree with Ms. Hottle that your siblings should contact an immigration attorney for a consult and more complete guidance than what we can accomplish in this forum.
You need legal advice. Legal advice requires a consultation. It's not the type of question that can be answered on Avvo, nor should it be. Call around.
IMPORTANT: Mr. Murray's response is NOT legal advice and does NOT create an attorney-client relationship. You should NOT rely on this response. Mr. Murray's response was generated without conducting a full inquiry as would occur during an attorney-client consultation. It is likely that the response above may be made less accurate, or become entirely inaccurate, as you, i.e. the questioner, disclose additional facts that should only be discussed during a private attorney-client consultation. I strongly recommend that you consult an attorney who is licensed to practice law in your state (or, in the case of immigration law, an attorney in ANY state), whereupon all relevant facts will be discussed. All responses posted by Mr. Murray on Avvo.com are intended as general information for the education of the public, and not for any specific individual. For persons located in New Jersey: To the extent that Mr. Murray's profile can be considered an advertisement in New Jersey, which is denied, be advised that NO ASPECT OF THIS ADVERTISEMENT HAS BEEN APPROVED BY THE SUPREME COURT OF NEW JERSEY. Furthermore, the selection methodology for the SuperLawyers' "Rising Stars" awards is set forth at length at this website: http://www.superlawyers.com/about/selection_process.html.
You need to retain an immigration attorney to handle these matters for you. Immigration law is constantly changing and mistakes can be very costly. No one can give you a course on this site on how to represent yourself. This is complex and beyond the scope of this site. If you have not already retained counsel, please feel free to contact me.
Leonard R. Boyer, Esq. 201-.675-.5577. Please be advised that the answer above is only general in nature cannot be construed as legal advice, given that not enough facts are known. It is your responsibility to retain a lawyer to analyze the facts specific to your particular situation in order to give you specific advice. Specific answers will require cognizance of all pertinent facts about your case. Any answers offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship.