LPR - Wish to adopt deceased brother's kids

Hi, I and my husband have no children and looking to raise my brother's kids aged 5 and 3. Current visa status: Legal Perm Resident Kids ages: 5 & 3 Kids' dad : My brother deceased December 2015 Kid's Mom: My brother's wife deceased May 2016 Kids Paternal grand father : Deceased Aug 2016 Kids' Paternal grand mother : Deaf and mute aged 65+ would not be able to care for kids alone. Kids Maternal side : Waived off rights for the kids Adoption completed in India in March 2017 Kids country of residence : India Questions: Since the demise of my brother I was in India for few months then returned back ( Dec - Jan ). Then again after my sister in law passed away I started living with the kids and took care of them since May 2016. I have just completed little over a year toward physical custody. Our legal adoption was done in March 2017. So does the other 2 year kick off only from March and end in March 2019? Will be able to apply for their immigration only in March 2019? Is there any other legal way to get the kids to US before that? On a B2 Visa or something. We would like to give the kids a family set up having dad / mom all under same roof so they get a schedule and come out of trauma sooner than later. Please help . Any input is greatly appreciated. Any good lawyer contact is also appreciated. Thanks, PrsBrs