Adopted Father, Biological Father, and the Child's Right to Know

Let's say Rohan's biological father, Vivek, left his pregnant wife, Suhani, before Rohan was born. Years later, when Rohan was 10, Vivek reappeared in his life and claimed that he wanted to be a part of Rohan's life. However, Rohan had already been living with his adoptive father, Prateek, whom his mother had married after Vivek left her. The twist - Suhani had also kept Rohan's biological fatherhood a secret from Prateek. Now, Prateek wants to know if he has any rights over Rohan or if Vivek can simply waltz in and claim custody. What would be the legal outcome under the Hindu Adoption and Maintenance Act, 1956 and the Guardians and Wards Act, 1890?