Are there any cases in NY where the Aunt and Uncle were granted visitation?

There are too many "ifs" did the aunt raise the child for 10 years acting as a parent, did they have guardianship at some point.

Is it merely though a divorce ?

No, it's a case of divorce between my sister in law and brother in law. I was very close to the children but now my sister in law rarely lets me see the kids. In fact I hadn't seen them in 4 years up until recently and because they were young then they don't remember me. I have gone to court for visitation but the judge said there is no presedence (?) for him to order visitation. I find it hard to believe that there has never been an Aunt & Uncle awarded visitation in NY.

Also, one of my nieces was recently in a group home which is how I regained connection with them and the workers/therapists thought is was a good idea for her to have more contact with family. She was in the group home for almost a year and shortly after we started visiting her there about every other week she was deemed well enough to go home so I believe our contact with her helped.

There is no law in NY that an aunt/uncle have to be awarded visitation.

I do not see this case setting precedent unless you have plenty of time and money and even then it's doubtful.

Why can't you visit with them when they are visiting with their father if the mother won't let you see them?

That's the question the Judge is going to ask you.

My Brother-in-law has no contact with the children

Then I see you having to wait until they are of legal age and then trying to establish (or re-establish) contact. This is a difficult legal situation but I do not think you can win.