I had an approved petition from my US citizen dad filed at Nebraska Service Center on May 1987. After 11-1/2 years my father died. 6 months after his death, my priority date became current. All my siblings (4 of them) are US citizens. They were petitioned by my mother who preceded my father in death. I am in the US continuously for 19 years. May I apply for humanitarian revalidation based on my father's petition? Any of my siblings can file affidavit of support on my behalf. What is the chance of approval on humanitarian revalidation cases?