My broher in law was with his wife (They are spilt up but not divorces) for 6 years. When he meet hershe was 6 months pregnant with her first child. No 6 years later he is the olny dad my niece knows. I was wondering if anyone knows that the chances are that he could get the child from her mother. They live in the same state and he sees he all the time. Matter of fact this week he has her all week, taking care of her and making sure she makes it to school everyday because his ex called and said that my niece was being bad and ahe can't handle her. With him being this involved dose anyone know in the state of Georgia what his rights are? Thank you for all your help.

Generally in the state of Georgia the biological presumption always prevail.If the mother contests his paternity and a DNA test shows he is not the biological father, all his rights will be terminated immediately.However he may be reimbursed for his past child support payments but it will be up to the judge.
O.C.G.A.§ 19-7-54

He is not the father and the mother and everyone arounds knows he is not the father. I was wondering if the fact that he has always been there and the fact that theare split up and he is still doing for my niece because her mother can't handle her if he would have a case? Oh yeah he is not on her birth certificate.

"De facto parent " doctrine is not recognized in Georgia,too.
The fact he he has always been there does not have any legal matter if the only reason is that she cannot handle her.
BTW what's the goal of it?

If he wants to become the primary custodian it will be a case "Parent vs. Third Party"
A third party may prevail only if he/she proves by clear and convincing evidence that the parent is unfit and his/her rights have to be terminated.
Grounds for TPR-Statute: §§ 15-11-58; 15-11-94
Abandonment or Extreme Parental Disinterest
Abuse/Neglect
Mental Illness or Deficiency
Alcohol or Drug Induced Incapacity
Felony Conviction/Incarceration
Failure of Reasonable Efforts
Failure to Maintain Contact
Failure to Provide Support

I guess you did not want to hear it but that's the Georgian law.