3 years ago when I was not a U.S citizen ,my uncle (U.S.citizen) applied for my Mom(his sister) for an immigrant visa,,,after 3 years, we received a letter from NVC (National Visa Center ) that she has been approved but apparently it would take forever , maybe 7-8 years to get a visa.
I decided to apply one more time for my parents eventhough, my Mom's application has been approved , maybe through my petition it would take less time for her and my Dad to come here.
everybody advises me that "Child applying for parents is faster than brother applying for sister...??? " is that right? and also is it possible to apply for my Mom since my Uncle already applied for her 3 years ago.????

thanks guys for your answers and comments