Are foster parents entitled to child custody over biological

Are foster parents, who raised a child for a decade, entitled to its permanent custody against the wishes of biological parents?. The Supreme Court is to decide this complex issue.
The apex court has agreed to hear a plea of biological parents seeking custody of their child who was allowed by the Delhi High Court to live with his uncle and aunt with whom he has been living for the last 10 years.
A bench headed by Justice Gyan Sudha Mishra issued notice to the foster parents on the plea of biological parents seeking custody of the 12-year old boy.

In this case, the child was taken by his maternal aunt in 2002 when he was two years old to be better looked after as his parents were not able to give time to the child due to their busy schedule.
The maternal aunt and her husband took the child as they had three daughters and did not have son. They promised to take care of him.
The child remained with them for nearly ten years and used to visit his biological parents on weekends and on holidays.

The biological parents then took the child back in May 2012.
In the meanwhile, the foster parents filed a complaint against the biological parents accusing them of illegally taking away the boy and also approached the Delhi High Court which directed them to produce the child.

The boy was produced before the court on August 1, 2012 and was sent with the foster parents.
On August 3, the High Court spoke to the boy and biological parents in chamber and the child expressed desire to live with his uncle and aunt.
The matter was then referred to mediation centre and all the parties reached an agreement wherein the biological parents agreed to let the child live with the relatives.
However, the biological parents now approached the apex court saying they had signed the documents under great depression and custody of child be given to them.
Advocate Subhashis R Soren, appearing for the biological parents, submitted that the High Court's order is bad in law and his clients should not be separated from their child.