My question involves a child custody case from the State of: Georgia/ Tenn/ Mass.

I am posting this about a friend.
Him and his ex-gf had twins at the age of 24, the girl 23. They were both in school (in Georgia) and attempted to get an abortion but found out it was twins. She really wanted to keep them and he though somehow they could make it work and he knew his parents would help out. During the pregnancy the girl went back and forth between staying with her (single) mother and the boyfriend. He took her to the doctor appointment, hosted her baby shower and was present at the delivery, cut the cords and signed birth certificates, etc. They never married. Once they were born he decided to go back home to Tennessee so the babies grandparents (his parents) could help. His parents helped take care of the new-borns, bought a minivan for them, paid off the girl’s credit card debt, etc. The girl couldn’t stand living in Tennessee away from her friends so after about a year they moved back to Georgia. They weren’t really getting along at this point the father working all the time and the mother very unhappy. It got to the point where she moves out to live in a girlfriend’s living room- with the two babies. The mother’s mom is nowhere in the picture even though she resides in Georgia. The mother of the twin’s- her reason for leaving is because she met someone. This new man lives in Massachusetts. He met the kids and they did the long distance thing. The mother files for child support because she needs money to put the kids in daycare so she can work. The father is really struggling and gets behind on child support and the mother refuses him visitation rights- Nothing legal just doesn’t pick up the phone or just says no you can’t see the kids and wants him to go through the legal process to get visitation right. She also slaps a domestic violence charge but drops it. The father doesn’t have the money for a lawyer and moves back to Tennessee to live with his parents for financial reasons.
Just recently(less than a year after the father moved back to TN) the mother decides to move to Massachusetts with the kids to live with the new boyfriend. She doesn’t even tell the father of her children she is leaving Georgia. He finds out through friends and calls her but again she refuses to let him see the kids. At this point the kids are 3 yrs old and live in Massachusetts.
So my question is what is the father’s rights because there is no legal custody or visitation court orders, only child support which he is up-to-date with. Is there any way for him to get the mother and the kids back to Georgia? The father wants to move back to Georgia and he wants to be there for his kids.