Getting custody in a different state

i am trying to get information for my brother. About 3 years ago he lost custody of his son in NY because he was into drugs and was found to be incompitant. In the last year and a half he has turned his life around. He has not used and also has a great job with health insurance that his son is covered by. He now lives in the Va and is unsure where he needs to file for custody. Is it NY or Va? Also what is the process forhim getting custody back. My sister has custody of the child now but is no better than my brother was 3 years ago. He has called the family court in NY with no luck. Please point me in the right direction so the kid can be where he needs to be.