If you just want them to come to visit, they need to apply for tourist visas and try to bring as much documentation with them as possible to show that they do not intend to immigrate to the US but that they will return to Mexico after the brief visit. Your parents can provide an affidavit of support for them but there is no guarantee that the visas will be granted just because of that. Please let me know if you have any additional questions or how I can be of further assistance to you in this matter.
Answered on Sep 23rd, 2014 at 1:50 AM