Relocation from Kentucky to Tennessee

My question involves a child custody case from the State of: KY

Background:
I have a niece that ran away from home (in TN) at the age of 17 with her 21 year old boyfriend. We called the police and reported her as a runaway and gave them an address of where we thought she was living (5.5 hours away in Eastern KY with the boyfriend and his parents). TN said they contacted the local police in KY, but nothing ever came of it. I'm not sure if it was because she had just turned 17 and they figured she was old enough, or if it was because the boyfriend's uncle is a sheriff where they moved to, and according to the boy he is "untouchable" in his uncle's jurisdiction....

Issue:
She has been in KY now for almost 2 years (she is 18 - getting ready to turn 19). Since she has been in KY she became pregnant and had a baby. She doesn't work and her boyfriend doesn't work - apparently his mother has been "teaching" them the joys of living off of the system (welfare). From what I understand they don't have a stable place to live, but rather move from place to place staying with whatever family member will have them.

Yesterday, my niece called her mother and said it wasn't working out and they are fighting all the time - she wants to come home. She asked her mother to come and get her and said that her boyfriend said she is not allowed to leave with the child.

Question:
Can she leave with the child? They were not married and nothing was ever done in court regarding the child, but he did sign the birth certificate when the child was born (which I believe automatically establishes paternity, doesn't it?). Can she legally leave and move the child across state lines? If she can leave, how can we go about getting the child out of the house? I would think, in a normal situation, you would go to the local law enforcement for help, but in this case I don't think the boyfriend's uncle would allow the child to leave either. They would be moving to TN - where there is a lot of family to help them out (mom, aunts, grandparents, etc...). They would have a place to live and no longer have to move around and would not have to "play" the system.

Can anyone offer advice on this totally messed up situation?

Any help is appreciated!

If paternity was established (which in most states requires signing an affidavit of paternity. Haven't checked TN process to verify) but the fact he is listed on the BC suggests that did take place. If nothing had been done other than that, mom is considered to have default custody of the child and can go where she chooses.

Dad can file a custody suit in TN though and since that is the current residence of the child, TN courts can require mom to return the child to TN.

How to get the child out of the house? That is a logistic question that nobody can answer. Unless she is never allowed to leave the house with the child in her arms, I would think that once she is out, she just keeps going until she reaches some pick up point pre-arranged with her mother.