Australian child custody laws....surely this cant be right?

my cousin and he partner seperated when her child was two....the grand mother of the child asked to have the 2 yr old for a few weeks in another state while my cousin sorted her living arrangements out after the seperation.At the time the child was ment to be sent back she found out the father of the child actually moved over with he's mum a week after the child arrived and together they decided not to give him back to the mother.She was intilted to legal aid but nothing ever happened....she kept regular conact on the phone.....hired a P.I (who ended up being dodgy) and she wasn't getting anywhere...she obviously had to continue living her life without the child.The grandmother and father moved to a different address and my cousin only had a phone number for the child,sometimes they dont answer.She asked if she could stay with them in there house if she gathered flight money as she couldnt afford accomodation..they said no.Its been 2 and a half years the child now goes to school in this other state...my cousin had another child recently..the boy wants to be a part of he's sibblings life..the father and grand mother got my cousin to sign papers and told her only if she signed them she could see her son for a few hours....a lawyer told her she basiclly had no chance to get him back(however the papers wern't handing over rights just saying she agreed to hand him back over after visits....she signed the papers and the grandmother bought the child to visit but did it in a public place and guarded them the whole time...the child cried that he wanted to stay with he's mum.he needs to be back with her....its been quite distressing for mother and child...has anyone been through anything like this ?? i want my cousin to get her son back...he's 5 yrs old aand he wants to be with he's mum....surely a wonderful mother cant have this happen to her...why cant she have him back..why do they get to have him in another state?? we all miss him...i do not think its right that a laywer can say...took too long cant get him back now...its her child she gave birth too...hy does the father and grand mother have this right to claim him and ruin everyones life?