回复：回复：父母b2 签证来美， I-130 已批， 如何在美国获得绿卡而不必回国？

If you try to use the humanitarian reasons to reinstate your parents green card application after the cases are revoked, you can ask your sister-in-law to be the sponsor if she is a US citizen.

Here is an article for the procedure to request humanitarian reinstatement of I-130 petitions that have been revoked based on the death of the petitioner

http://www.visalawyerblog.com/2009/09/death_of_us_petitioner_visa_sp.html